Use gcc as the default C compiler if CC is not set.

diff --git a/giscanner/__init__.py b/giscanner/__init__.py
index 7c2f365a..607fe341 100644
--- a/giscanner/__init__.py
+++ b/giscanner/__init__.py
@@ -21,6 +21,8 @@ import os
 builddir = os.environ.get('UNINSTALLED_INTROSPECTION_BUILDDIR')
 if builddir is not None:
     __path__.append(os.path.join(builddir, 'giscanner'))  # type: ignore  # mypy issue #1422
+if not 'CC' in os.environ:
+    os.environ['CC'] = 'gcc'
 try:
     from ._version import __version__
 except ImportError:
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<div class='path'>path: <a href='/guix/log/?id=fe1d2393a1f5fb729a4a3b8889645e32c35ada8c'>root</a>/<a href='/guix/log/gnu?id=fe1d2393a1f5fb729a4a3b8889645e32c35ada8c'>gnu</a>/<a href='/guix/log/gnu/packages?id=fe1d2393a1f5fb729a4a3b8889645e32c35ada8c'>packages</a>/<a href='/guix/log/gnu/packages/haxe.scm?id=fe1d2393a1f5fb729a4a3b8889645e32c35ada8c'>haxe.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/packages/haxe.scm?id=fe1d2393a1f5fb729a4a3b8889645e32c35ada8c&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-04-28 10:11:25 -0400'>2024-04-28</span></td><td><a href='/guix/commit/gnu/packages/haxe.scm?id=4c81c1f734ee2979f42671cb15fe83be64c06b6c'>gnu: hashlink: Update to 1.14</a><span class='msg-avail'>...<span class='msg-tooltip'>Change-Id: I1fe593cc03675cce81f70efb2576ff7bcd374187
Signed-off-by: Maxim Cournoyer &lt;maxim.cournoyer@gmail.com&gt;
</span></span></td><td>Vasilii Smirnov</td></tr>
<tr><td><span title='2024-04-28 10:11:25 -0400'>2024-04-28</span></td><td><a href='/guix/commit/gnu/packages/haxe.scm?id=2205660ce2f78ae608c28de8d289b7848464928b'>gnu: haxe: Update to 4.3.4</a><span class='msg-avail'>...<span class='msg-tooltip'>Note that the ocaml-luv library has made a few breaking changes, while
only updating the PATCH number in their version. As of now, haxe can
only be compiled with the 0.5.12 version of ocaml-luv - no lower, no
higher.

Change-Id: I465191aa8db806275b2385d11a602dfb0d8d4bb9
Signed-off-by: Maxim Cournoyer &lt;maxim.cournoyer@gmail.com&gt;
</span></span></td><td>Vasilii Smirnov</td></tr>
<tr><td><span title='2024-02-05 13:56:31 +0800'>2024-02-05</span></td><td><a href='/guix/commit/gnu/packages/haxe.scm?id=2b296427d7bd7b6b155e0e94403c1227ce014008'>gnu: mbedtls-apache: Rename to mbedtls-lts.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/tls.scm (mbedtls-apache): Rename package to "mbedtls".
Rename variable to…
(mbedtls-lts): …this.
(mbedtls-apache): Define as deprecated by mbedtls-lts.
(mbedtls-for-hiawatha): Adjust accordingly.
* doc/guix.texi: Likewise.
* gnu/packages/emulators.scm (dolphin-emu,retroarch)[inputs]: Likewise.
* gnu/packages/game-development.scm (godot-lts,godot)[inputs]: Likewise.
* gnu/packages/hardware.scm (hueplusplus,openrgb)[inputs]: Likewise.
* gnu/packages/haxe.scm (neko,haxe,hashlink)[inputs]: Likewise.
* gnu/packages/irc.scm (inspircd)[inputs]: Likewise.
* gnu/packages/julia-jll.scm (julia-mbedtls-jll)[arguments]&lt;#:phases&gt;,[inputs]:
Likewise.
* gnu/packages/julia.scm (julia)[arguments]&lt;#:phases&gt;,[inputs]: Likewise.
* gnu/packages/linphone.scm (bctoolbox)[inputs]: Likewise.
* gnu/packages/linux.scm (dislocker)[inputs]: Likewise.
* gnu/packages/networking.scm (nng)[inputs]: Likewise.
* gnu/packages/search.scm (dataparksearch)[inputs]: Likewise.
* gnu/packages/video.scm (obs)[inputs]: Likewise.
* gnu/packages/web.scm (hiawatha)[arguments]&lt;#:phases&gt;: Likewise.

Change-Id: I0c58b3cd0bcf6e44e7b16a69f6d2739aa3c1545b
</span></span></td><td>Hilton Chain</td></tr>