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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<tr><td><span title='2018-11-01 08:20:13 +0100'>2018-11-01</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=ee3dd7a83af94ce19ce4909b15cecc57a5c99cde'>gnu: sdl2: Update to 2.0.9.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/sdl.scm (sdl2): Update to 2.0.9.
</span></span></td><td>Rutger Helling</td></tr>
<tr><td><span title='2018-10-27 20:08:50 +0200'>2018-10-27</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=763d44920dc1ae8a1ea2ff5aab58fdf818182880'>gnu: guile-sdl2: Update to 0.3.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/sdl.scm (guile-sdl2): Update to 0.3.1.
</span></span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2018-10-01 12:12:23 +0200'>2018-10-01</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=21be24b74f1a0cac185637620d59a3764c539875'>gnu: Add ghc-sdl2-image.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/sdl.scm (ghc-sdl2-image): New variable.
</span></span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2018-10-01 12:12:22 +0200'>2018-10-01</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=d975534e856dc6c8426d9f28af3b5d30ead31ac3'>gnu: Add ghc-sdl2-mixer.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/sdl.scm (ghc-sdl2-mixer): New variable.
</span></span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2018-10-01 12:12:22 +0200'>2018-10-01</span></td><td><a href='/guix/commit/gnu/packages/sdl.scm?id=62dd7171d3fa3df964f34ebb1627704ea447cc21'>gnu: Add ghc-sdl2.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/sdl.scm (ghc-sdl2): New variable.
</span></span></td><td>Ricardo Wurmus</td></tr>