Patch adapted from Sage. Allows building ECL on libffi 3.3.
diff --git a/src/c/ffi.d b/src/c/ffi.d
index 8861303e..8a959c23 100644
--- a/src/c/ffi.d
+++ b/src/c/ffi.d
@@ -133,8 +133,8 @@ static struct {
 #elif defined(X86_WIN64)
   {@':win64', FFI_WIN64},
 #elif defined(X86_ANY) || defined(X86) || defined(X86_64)
-  {@':cdecl', FFI_SYSV},
-  {@':sysv', FFI_SYSV},
+  {@':cdecl', FFI_UNIX64},
+  {@':sysv', FFI_UNIX64},
   {@':unix64', FFI_UNIX64},
 #endif
 };
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<div class='path'>path: <a href='/guix/log/?id=5495e880a6e1000a78c50f3cefa0c0b2ee8ee1c8'>root</a>/<a href='/guix/log/nix?id=5495e880a6e1000a78c50f3cefa0c0b2ee8ee1c8'>nix</a>/<a href='/guix/log/nix/libutil?id=5495e880a6e1000a78c50f3cefa0c0b2ee8ee1c8'>libutil</a>/<a href='/guix/log/nix/libutil/util.hh?id=5495e880a6e1000a78c50f3cefa0c0b2ee8ee1c8'>util.hh</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/nix/libutil/util.hh?id=5495e880a6e1000a78c50f3cefa0c0b2ee8ee1c8&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-09-14 15:42:55 +0200'>2020-09-14</span></td><td><a href='/guix/commit/nix/libutil/util.hh?id=ee9dff34f9317509cb2b833d07a0d5e01a36a4ae'>daemon: Move 'Agent' to libutil.</a><span class='msg-avail'>...<span class='msg-tooltip'>* nix/libstore/build.cc (DerivationGoal::tryBuildHook): Add "offload" to
'args' and pass settings.guixProgram as the first argument to
Agent::Agent.
(pathNullDevice, commonChildInit, Agent, Agent::Agent)
(Agent::~Agent): Move to...
* nix/libutil/util.cc: ... here.
* nix/libutil/util.hh (struct Agent, commonChildInit): New
declarations.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-01-12 00:19:09 +0100'>2020-01-12</span></td><td><a href='/guix/commit/nix/libutil/util.hh?id=7033c7692ccbbbad8f7b9952015de071a5588e87'>daemon: Account for deleted store files when deduplication is on.</a><span class='msg-avail'>...<span class='msg-tooltip'>Previously, a store item that is a regular file would not be accounted
for in the 'bytesFreed' value computed by 'deletePath' because its
'st_nlink' count would always be &gt;= 2.  This commit fixes that.

* nix/libutil/util.hh (deletePath): Add optional 'linkThreshold' argument.
* nix/libutil/util.cc (_deletePath): Add 'linkThreshold' argument and
honor it.  Pass it down in recursive call.
(deletePath): Add 'linkThreshold' and honor it.
* nix/libstore/gc.cc (LocalStore::deleteGarbage): Pass 'linkThreshold'
argument to 'deletePath', with a value of 2 when PATH is a store item
and deduplication is on.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-08-18 11:31:28 +0200'>2017-08-18</span></td><td><a href='/guix/commit/nix/libutil/util.hh?id=ed464f48efd80e6439441d7a9f6d0e7988fb1272'>nix: Remove unused function.</a><span class='msg-avail'>...<span class='msg-tooltip'>* nix/libutil/util.hh:
* nix/libutil/util.cc (decodeOctalEscaped): Remove unused and buggy function.
</span></span></td><td>Andy Wingo</td></tr>