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

diff -ru gobject-introspection-1.58.1.orig/giscanner/__init__.py gobject-introspection-1.58.1/giscanner/__init__.py
--- gobject-introspection-1.58.1.orig/giscanner/__init__.py	1970-01-01 01:00:00.000000000 +0100
+++ gobject-introspection-1.58.1/giscanner/__init__.py	2018-12-03 13:33:28.788971299 +0100
@@ -22,6 +22,8 @@
 builddir = os.environ.get('UNINSTALLED_INTROSPECTION_BUILDDIR')
 if builddir is not None:
     __path__.append(os.path.join(builddir, 'giscanner'))
+if not 'CC' in os.environ:
+    os.environ['CC'] = 'gcc'
 try:
     from ._version import __version__
 except ImportError:
52015c9498128fd82a36fa153046e7a'/><select name='h' onchange='this.form.submit();'>
<option value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
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<div class='path'>path: <a href='/guix/log/?id=ccfae528552015c9498128fd82a36fa153046e7a'>root</a>/<a href='/guix/log/build-aux?id=ccfae528552015c9498128fd82a36fa153046e7a'>build-aux</a>/<a href='/guix/log/build-aux/compile-all.scm?id=ccfae528552015c9498128fd82a36fa153046e7a'>compile-all.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/build-aux/compile-all.scm?id=ccfae528552015c9498128fd82a36fa153046e7a&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-06-23 23:35:27 +0200'>2021-06-23</span></td><td><a href='/guix/commit/build-aux/compile-all.scm?id=ef82ba9dd94369926eb13325d5e7da4306d23dd7'>build: Makefile splits Scheme compilation in four steps.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://bugs.gnu.org/48963&gt;.
Reported by Julien Lepiller &lt;julien@lepiller.eu&gt;.

This reduces peak memory consumption to something less unreasonable.

* Makefile.am (make-go): Depend on 'make-*-go' targets; remove body.
(guile-compilation-rule): New function.
(MODULES_CORE, MODULES_PACKAGES, MODULES_SYSTEM, MODULES_CLI): New
variables.
&lt;top level&gt;: Call 'guile-compilation-rule' 4 times.
* build-aux/compile-all.scm &lt;top level&gt;: Expect "--total" and
"--processed".  Take them into account when displaying progress
reports.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-06-18 14:18:06 +0200'>2021-06-18</span></td><td><a href='/guix/commit/build-aux/compile-all.scm?id=003728cfab907be5df1411c5faaf466a2b8d5ba2'>build: Remove Guile 2.2 workaround.</a><span class='msg-avail'>...<span class='msg-tooltip'>* build-aux/compile-all.scm &lt;top level&gt;: Remove Guile 2.2 workaround.
</span></span></td><td>Ludovic Courtès</td></tr>