This patch is borrowed from Debian's patches for plink

Author: Peter Green <plugwash@p10link.net>
Puropose: Fallback to endian.h if all else fails on 64bit machines
Closes: #528659
Forwarded: Shaun Purcell <plink@chgr.mgh.harvard.edu>
License: same as plink itself.
===================================================================
--- plink-1.06.orig/Rsrv.h	2009-05-15 03:35:29.000000000 +0100
+++ plink-1.06/Rsrv.h	2009-05-15 03:35:41.000000000 +0100
@@ -313,7 +313,18 @@
 #define __BIG_ENDIAN__ 1
 #define SWAPEND 1
 #elif ! defined Win32 /* Windows is little-endian is most cases, anywhere else we're stuck */
-#error "Cannot determine endianness. Make sure config.h is included or __{BIG|LITTLE}_ENDIAN__ is defined ."
+  //try endian.h before we finally bail out
+  #include <endian.h>
+  #if __BYTE_ORDER == __LITTLE_ENDIAN
+    #warning using little endian based on information from endian.h
+    #define __LITTLE_ENDIAN__ 1
+  #elif __BYTE_ORDER == __BIG_ENDIAN
+    #warning using big endian based on information from endian.h
+    #define __BIG_ENDIAN__ 1
+    #define SWAPEND 1
+  #else    
+    #error "Cannot determine endianness. Make sure config.h is included or __{BIG|LITTLE}_ENDIAN__ is defined ."
+  #endif    
 #endif
 
 /* FIXME: all the mess below needs more efficient implementation - the current one is so messy to work around alignment problems on some platforms like Sun and HP 9000 */
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<div class='path'>path: <a href='/guix/log/?id=1fb51bd5af7d673cb3c01c5e16d44380d84237fe'>root</a>/<a href='/guix/log/gnu?id=1fb51bd5af7d673cb3c01c5e16d44380d84237fe'>gnu</a>/<a href='/guix/log/gnu/tests.scm?id=1fb51bd5af7d673cb3c01c5e16d44380d84237fe'>tests.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/tests.scm?id=1fb51bd5af7d673cb3c01c5e16d44380d84237fe&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-05-18 22:29:54 +0200'>2022-05-18</span></td><td><a href='/guix/commit/gnu/tests.scm?id=9a5d68692314bebd16dbcdc0d4e4e52fa4d5812f'>services: Add more description fields.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-08-29 01:05:26 -0400'>2021-08-29</span></td><td><a href='/guix/commit/gnu/tests.scm?id=da4e40948326387d5bcda58783914d5f9ce8b095'>Migrate to the new 'targets' field of bootloader-configuration.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-04-12 18:42:22 +0200'>2021-04-12</span></td><td><a href='/guix/commit/gnu/tests.scm?id=3332f4365bf329c361d650c70e53b8a74ad923bd'>tests: Support package extensions in the backdoor REPL.</a><span class='msg-avail'>...</span></td><td>Maxime Devos</td></tr>
<tr><td><span title='2021-02-19 20:10:08 +0100'>2021-02-19</span></td><td><a href='/guix/commit/gnu/tests.scm?id=f57b7cea748c1e8284373811c13398d9f69aec89'>tests: Export %simple-os.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
 "guix build /….drv" correctly for non-existent derivations.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-11-17 23:14:54 +0100'>2019-11-17</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=16ac74033ae9f01e8be81c4f7f1857e13545bc2f'>tests: Test "guix build /gnu/store/….drv".</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-11-07 18:39:55 +0100'>2019-11-07</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=537b2daba9a5f0c17bde2203e6fb074a661d5b32'>gnu: commencement: Ensure 'gnu-make-final' refers to the native 'pkg-config'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-07-20 01:32:17 +0200'>2019-07-20</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=723bdb8ef0175716a2bfa93e96c3fd757d7b2679'>ui: 'warn-about-load-error' provides hints for unbound variables.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-07-20 01:32:17 +0200'>2019-07-20</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=a2a94b6e58e5120462d6861bdf72efa2170bfd73'>ui: 'warn-about-load-error' warns about file/module name mismatches.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-04-19 17:46:40 +0200'>2019-04-19</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=ea261dea0c581771b4cf297e983f7addc6807051'>guix build: Accept multiple '-s' options.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-04-15 16:57:12 +0200'>2019-04-15</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=4aea820f0954fce4d076718072faf211f62f3f9d'>guix build: Fix relative file name canonicalization for '--root'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-02-04 00:03:30 +0100'>2019-02-04</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=a87d66f371da2a84d7bba1cae58b71c9c9af73aa'>daemon: Rename 'NIX_STATE_DIR' and 'NIX_DB_DIR' environment variables.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-10-09 18:54:12 +0200'>2018-10-09</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=b33e191c86b7638517ea838b63a54d031a033554'>guix build: '-f' accepts file-like objects.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-05-04 15:07:08 +0200'>2018-05-04</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=2d2f98efb36db3f003d950a004806234962b4f4d'>guix build: Nicely report unbound variables with hints.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-03-13 20:17:06 +0200'>2018-03-13</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=64f925cb4bb726b07e1d115e1132688ca47bdefe'>gnu: time: Update to 1.9.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2017-11-11 15:33:04 +0100'>2017-11-11</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=4ad3a3f995dc9bd00edbe37eb773bf07d1ad14c0'>tests: Refer to "time@1.8".</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>