[gjs/meson.msvc: 3/3] installed-tests/js/meson.build: Fix building test DLLs

[Chun-wei Fan <fanchunwei src gnome org>]

commit 5e1c1e8f34d43ed671e0a62429c9aa7b2da637fd
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Oct 25 17:17:11 2019 +0800

    installed-tests/js/meson.build: Fix building test DLLs
    
    The test DLLs, in which the sources are provided by
    GObject-Introspection, need to be built with _GI_EXTERN properly
    overridden on MSVC builds so that the symbols in those test DLLs are
    exported properly, so that we can build the introspection files for them
    properly when building the minijasmine test program.

 installed-tests/js/meson.build | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)
---
diff --git a/installed-tests/js/meson.build b/installed-tests/js/meson.build
index bbb882a5..0237244b 100644
--- a/installed-tests/js/meson.build
+++ b/installed-tests/js/meson.build
@@ -15,9 +15,16 @@ minijasmine = executable('minijasmine', '../minijasmine.cpp',
 gidatadir = gi.get_pkgconfig_variable('gidatadir')
 gi_tests = gidatadir / 'tests'
 
+test_gir_extra_c_args = []
+
+# We need to ensure the symbols in the test DLLs export in MSVC builds
+if cc.get_id() == 'msvc'
+  test_gir_extra_c_args += ['-D_GI_EXTERN=__declspec(dllexport)extern']
+endif
+
 regress_dependencies = [glib, gobject, gio]
 regress_gir_includes = ['Gio-2.0']
-regress_gir_c_args = []
+regress_gir_c_args = test_gir_extra_c_args
 if build_cairo
     regress_gir_includes += 'cairo-1.0'
     regress_dependencies += [cairo, cairo_gobject]
@@ -46,7 +53,8 @@ warnlib_sources = [
 ]
 libwarnlib = library('warnlib', warnlib_sources,
     dependencies: [glib, gobject, gio], install: get_option('installed_tests'),
-    install_dir: pkglibdir)
+    install_dir: pkglibdir,
+    c_args:  test_gir_extra_c_args)
 # This should have --warn-all turned off, but there is currently no way to do so
 # in gnome.generate_gir(). See https://github.com/mesonbuild/meson/issues/5876
 warnlib_gir = gnome.generate_gir(libwarnlib, includes: ['Gio-2.0'],
@@ -62,6 +70,7 @@ gimarshallingtests_sources = [
 ]
 libgimarshallingtests = library('gimarshallingtests',
     gimarshallingtests_sources, dependencies: [glib, gobject, gio],
+    c_args:  test_gir_extra_c_args,
     install: get_option('installed_tests'), install_dir: pkglibdir)
 gimarshallingtests_gir = gnome.generate_gir(libgimarshallingtests,
     includes: ['Gio-2.0'], sources: gimarshallingtests_sources,