[gimp] build: (meson) fix CC_VERSION contains backslashes on Windows.

[Jehan <jehanp src gnome org>]

commit a084032c59668108e9eaf05c1f6a1c66dcfbe8a2
Author: Jacob Boerema <jgboerema gmail com>
Date:   Sat Aug 22 14:35:43 2020 -0400

    build: (meson) fix CC_VERSION contains backslashes on Windows.
    
    This caused an invalid specifier warning in gimp-version.c and an
    incorrect value of COLLECT_GCC reported by gimp -v.

 meson.build | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/meson.build b/meson.build
index e20ca7d30f..a4958d2ec3 100644
--- a/meson.build
+++ b/meson.build
@@ -1406,6 +1406,11 @@ if cc_version == ''
   # compiler. Just save its name and version.
   cc_version = cc.get_id() + ' ' + cc.version()
 else
+  if platform_windows
+    # On Windows the CC_VERSION string can contain backslashes in paths,
+    # specifically in COLLECT_GCC. Replace by slashes.
+    cc_version = '/'.join(cc_version.split('\\'))
+  endif
   # See also: https://github.com/mesonbuild/meson/pull/6179
   cc_version = '\\n'.join(cc_version.split('\n'))
 endif