glib-compile-resources: Fix exporting on Visual Studio

Have the generated .c code decorate the prototypes with "G_MODULE_EXPORT"
instead of "extern" when --internal is not being used, so that we also
export the symbols from the generated code on Visual Studio-style
compilers.  If --internal is used, we decorate the prototypes with
"G_GNUC_INTERNAL", as we did before.

Note that since the generated .c code does not attempt to include the
generated headers (if one is also generated), the gnerated headers are
still generated as they were before.
14 jobs for backport-1468-compile-resources-win32 in 36 minutes and 5 seconds
Status Job ID Name Coverage
  Style Check
passed #754031
check-todos

00:01:08

failed #754030
allowed to fail
style-check-diff

00:01:14

 
  Build
passed #754036
cross-android_api21_arm64

00:07:46

passed #754037
cross-android_api28_arm64

00:09:13

passed #754038
cross-mingw64

00:06:15

passed #754033
debian-stable-x86_64

00:09:58

passed #754032
fedora-x86_64

00:19:48

passed #754035
G_DISABLE_ASSERT

00:11:34

passed #754034
installed-tests

00:12:12

passed #754039
win32-ps
msys2-mingw32

00:11:10

passed #754040
win32-ps
vs2017-x64

00:08:30

 
  Coverage
passed #754041
coverage

00:01:53

78.2%
 
  Analysis
passed #754043
scan-build

00:07:41

failed #754042
allowed to fail
valgrind

00:13:08

 
Name Stage Failure
failed
valgrind Analysis
Uploading artifacts...
_build/config.h: found 1 matching files

_build/glib/glibconfig.h: found 1 matching files

_build/meson-logs: found 7 matching files

Uploading artifacts to coordinator... ok
id=754042 responseStatus=201 Created token=NxgFZ94x
Uploading artifacts...
_build/valgrind-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=754042 responseStatus=201 Created token=NxgFZ94x
ERROR: Job failed: exit code 1
failed
style-check-diff Style Check
 #        ifdef DLL_EXPORT
-# define GOBJECT_VAR extern __declspec(dllexport)
+#define GOBJECT_VAR extern __declspec(dllexport)
# else /* !DLL_EXPORT */
# define GOBJECT_VAR extern
# endif /* !DLL_EXPORT */
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1