as-macros-private.h: Define macros for visibility for clang-cl

On clang-cl (i.e. Visual Studio-like meaning _MSC_VER is defined) builds,
symbols in shared builds have visibility to be hidden by default, and
decorating symbols with GCC's default visibility is not enough to export the
symbol.

Some private symbols must still be exported from the appstream DLL for the
tools and tests, so define versions of the visibility macros that are suitable
for use for clang-cl, and add another (private) macro that is used to export
symbols that do not fall into sections where we explicitly want visibility to
be hidden.

Consequently, use the macros in as-desktop-entry.h so that we don't fall into
the situation where clang-cl complains as we are attempting to do a
__declspec(dllexport) in a hidden visibility section.

src/as-desktop-entry.h

@@ -27,8 +27,7 @@
 #include "as-metadata.h"
 #include "as-utils-private.h"
 
-G_BEGIN_DECLS
-#pragma GCC visibility push(hidden)
+AS_BEGIN_PRIVATE_DECLS
 
 typedef GPtrArray *(*AsTranslateDesktopTextFn) (const GKeyFile *de,
 						const gchar    *text,
@@ -54,7 +53,6 @@ gboolean	       as_desktop_entry_parse_file (AsComponent		    *cpt,
 						    gpointer		     user_data,
 						    GError		   **error);
 
-#pragma GCC visibility pop
-G_END_DECLS
+AS_END_PRIVATE_DECLS
 
 #endif /* __AS_DESKTOP_ENTRY_H */

src/as-macros-private.h

@@ -26,6 +26,21 @@
 #include "as-macros.h"
 
 G_BEGIN_DECLS
+
+#ifdef _MSC_VER
+
+#define AS_BEGIN_PRIVATE_DECLS G_BEGIN_DECLS
+#define AS_END_PRIVATE_DECLS G_END_DECLS
+
+#ifdef AS_STATIC
+#else
+#define AS_INTERNAL_VISIBLE __declspec(dllexport)
+#endif
+
+#define AS_INTERNAL_API AS_INTERNAL_VISIBLE
+
+#else
+
 #pragma GCC visibility push(hidden)
 
 #define AS_BEGIN_PRIVATE_DECLS \
@@ -35,6 +50,9 @@ G_BEGIN_DECLS
 #define AS_END_PRIVATE_DECLS _Pragma ("GCC visibility pop") G_END_DECLS
 
 #define AS_INTERNAL_VISIBLE __attribute__((visibility("default")))
+#define AS_INTERNAL_API
+
+#endif
 
 /**
  * as_str_equal0:
@@ -107,7 +125,10 @@ G_BEGIN_DECLS
 	}                                                  \
 	G_STMT_END
 
+#ifndef _MSC_VER
 #pragma GCC visibility pop
+#endif
+
 G_END_DECLS
 
 #endif /* __AS_MACROS_PRIVATE_H */