Use 'uname -m', which in practice returns the processor architecture.

--- psm-3.3/buildflags.mak~	2014-08-20 21:00:18.000000000 +0100
+++ psm-3.3/buildflags.mak	2017-10-22 12:02:12.855291447 +0100
@@ -38,7 +38,7 @@
 endif
 
 export os ?= $(shell uname -s | tr '[A-Z]' '[a-z]')
-export arch := $(shell uname -p | sed -e 's,\(i[456]86\|athlon$$\),i386,')
+export arch := $(shell uname -m | sed -e 's,\(i[456]86\|athlon$$\),i386,')
 
 CC ?= gcc
 
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<tr><td><span title='2020-10-31 23:16:43 +0100'>2020-10-31</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=bfe82fe2f6e9f34c0774fe2114cdc7e937ba8bd2'>pack: Relocatable wrapper leaves root available to child processes.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-10-30 10:00:29 -0500'>2020-10-30</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=a73896425e92e5162766afdf042748b18f2462af'>guix: pack: Fix offset calculation for store directory mount point.</a><span class='msg-avail'>...</span></td><td>Eric Bavier</td></tr>
<tr><td><span title='2020-08-27 19:58:16 +0200'>2020-08-27</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=28dce8f02db38a41e59ecdf3786baa6f732636ff'>pack: fakechroot: Honor $LD_LIBRARY_PATH.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-07-28 14:41:05 +0200'>2020-07-28</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=c088aa2988ef82289c87ebfd6d07d8f1464dd8f0'>pack: "fakechroot" engine always creates its store.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-07-28 14:41:04 +0200'>2020-07-28</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=c6c0d5a22c2ee3d7164dab0129b2e4852a4ae76c'>pack: "fakechroot" execution engine can load its audit module.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-14 17:21:27 +0200'>2020-05-14</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=6456232164890dbf5aa20394ee24637feb4b7b9e'>pack: Add relocation via ld.so and fakechroot.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-14 17:21:27 +0200'>2020-05-14</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=0cd13e72f2a1f85ad6facc485248685276981d63'>pack: Factorize store references in wrapper.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-14 17:21:27 +0200'>2020-05-14</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=fde2aec3f498d5ec6db2121d72068e2b203e86cd'>pack: Wrapper honors 'GUIX_EXECUTION_ENGINE' environment variable.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-07 23:52:25 +0200'>2020-05-07</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=bdb9b4e8d3ebbc50f4725af12d91df300de05d15'>pack: Factorize 'exec_in_user_namespace' wrapper.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-07 23:52:25 +0200'>2020-05-07</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=14928af2af501516aba13d569eae0853e769fb91'>pack: Add 'xmalloc' in wrapper.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-07 23:52:25 +0200'>2020-05-07</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=4a53c19a325e7192c5aa6b0b34daf660ea615e17'>pack: Fix off-by-one in PRoot handling in the wrapper.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-04-24 16:21:13 +0200'>2020-04-24</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=2520059bdb43fa1663ce102f3f4c442d4918c32b'>pack: 'guix pack -R' wrapper correctly reports exit code.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-03-15 23:27:59 +0100'>2019-03-15</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=99aec37a78e7be6a591d0e5b7439896d669a75d1'>pack: "-RR" produces PRoot-enabled relocatable binaries.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-05-11 18:42:42 +0200'>2018-05-11</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=30da3173d5ee69777d0e1de4f9c977dea72e8a77'>pack: Relocatable wrapper now properly maps the current UID/GID.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-05-10 14:53:57 +0200'>2018-05-10</span></td><td><a href='/guix/commit/gnu/packages/aux-files/run-in-namespace.c?id=47a60325ca650e8fc1a291c8655b4297f4de8deb'>pack: Add '--relocatable'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>