The patch fixes build failure of form:
     ../src/alpha/osf.S:298:2: error: #error "osf.S out of sync with ffi.h"
Upstream fixed the bug in a more invasive way
but didn't have releases since 3.2.1.

The patch is taken from Gentoo:
https://gitweb.gentoo.org/repo/gentoo.git/tree/dev-libs/libffi/files/libffi-3.2.1-complex_alpha.patch

--- libffi-3.2.1/src/alpha/osf.S	2015-01-16 10:46:15.000000000 +0100
+++ libffi-3.2.1/src/alpha/osf.S	2015-01-16 10:46:24.000000000 +0100
@@ -279,6 +279,7 @@
 	.gprel32 $load_64	# FFI_TYPE_SINT64
 	.gprel32 $load_none	# FFI_TYPE_STRUCT
 	.gprel32 $load_64	# FFI_TYPE_POINTER
+	.gprel32 $load_none	# FFI_TYPE_COMPLEX
 
 /* Assert that the table above is in sync with ffi.h.  */
 
@@ -294,7 +295,8 @@
 	|| FFI_TYPE_SINT64 != 12	\
 	|| FFI_TYPE_STRUCT != 13	\
 	|| FFI_TYPE_POINTER != 14	\
-	|| FFI_TYPE_LAST != 14
+	|| FFI_TYPE_COMPLEX != 15       \
+	|| FFI_TYPE_LAST != 15
 #error "osf.S out of sync with ffi.h"
 #endif
 
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<div class='path'>path: <a href='/guix/log/?id=fa75b73501c9cc5daeabecccae2fe6d3a81adf3b'>root</a>/<a href='/guix/log/etc?id=fa75b73501c9cc5daeabecccae2fe6d3a81adf3b'>etc</a>/<a href='/guix/log/etc/disarchive-manifest.scm?id=fa75b73501c9cc5daeabecccae2fe6d3a81adf3b'>disarchive-manifest.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/etc/disarchive-manifest.scm?id=fa75b73501c9cc5daeabecccae2fe6d3a81adf3b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-08-06 23:14:41 +0200'>2022-08-06</span></td><td><a href='/guix/commit/etc/disarchive-manifest.scm?id=eab5366e679c149cf0a5abeb9a196700b171d9da'>disarchive-manifest: Exclude the Chromium tarball.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/disarchive-manifest.scm (disarchive-collection): Exclude
"chromium-" tarballs.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-08-05 15:28:02 +0200'>2022-08-05</span></td><td><a href='/guix/commit/etc/disarchive-manifest.scm?id=6d4a0ccecb58c62a95f7f36fa2f4fa53dd52312e'>disarchive-manifest: Filter out origins without a hash.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/disarchive-manifest.scm (disarchive-collection): Filter out
origins with a phony hash.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-08-05 00:14:29 +0200'>2022-08-05</span></td><td><a href='/guix/commit/etc/disarchive-manifest.scm?id=2acffd56a58c01785ea6ea738b79991c0685d364'>disarchive-manifest: Handle tar.xz archives.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/disarchive-manifest.scm (tarball-origin?): Add ".tar.xz".
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-10-09 01:02:18 +0200'>2021-10-09</span></td><td><a href='/guix/commit/etc/disarchive-manifest.scm?id=2ad1ef844632b7605ad6dd362e947a122a0a3925'>disarchive-manifest: Provide valid 'version' string.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/disarchive-manifest.scm &lt;top level&gt;: Turn 'version' field into a
string.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-09-14 11:50:58 +0200'>2021-09-14</span></td><td><a href='/guix/commit/etc/disarchive-manifest.scm?id=98712c14fe3517a48603a12eb2e64db305a54fe5'>etc: Add 'disarchive-manifest.scm'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/disarchive-manifest.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.
</span></span></td><td>Ludovic Courtès</td></tr>