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.
25 jobs for fix-gresource-export-msvc in 75 minutes and 57 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Style Check
passed #733410
check-todos

00:00:37

failed #735576
allowed to fail
style-check-diff

00:00:42

failed #733409
allowed to fail
style-check-diff

01:00:02

 
  Build
passed #733415
cross-android_api21_arm64

00:01:16

passed #733416
cross-android_api28_arm64

00:01:53

passed #733417
cross-mingw64

00:13:24

passed #733452
debian-stable-x86_64

00:15:09

passed #733449
fedora-x86_64

00:08:18

passed #733420
freebsd-11
freebsd-11-x86_64

00:05:19

passed #733421
freebsd-12
freebsd-12-x86_64

00:05:23

passed #735547
G_DISABLE_ASSERT

00:07:14

passed #735546
installed-tests

00:10:05

passed #733422
macos
macos

00:03:53

passed #733418
win32-ps
msys2-mingw32

00:09:05

passed #733419
win32-ps
vs2017-x64

00:07:58

failed #733412
debian-stable-x86_64

00:02:34

passed #733450
debian-stable-x86_64

00:14:48

failed #733411
fedora-x86_64

00:07:51

failed #733448
G_DISABLE_ASSERT

00:02:06

failed #733451
G_DISABLE_ASSERT

01:00:01

failed #733414
G_DISABLE_ASSERT

00:02:40

failed #733413
installed-tests

01:00:01

 
  Coverage
passed #733423
coverage

00:01:43

78.2%
 
  Analysis
passed #733425
scan-build

00:12:01

failed #733424
allowed to fail
valgrind

00:26:31

 
Name Stage Failure
failed
style-check-diff Style Check
+                     export, c_name, c_name,
+ export, c_name, c_name);
+ }
else
{
g_fprintf (file, "%s", gconstructor_code);
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1
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=733424 responseStatus=201 Created token=4WPozssQ
Uploading artifacts...
_build/valgrind-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=733424 responseStatus=201 Created token=4WPozssQ
ERROR: Job failed: exit code 1