contrib: use winstorecompat when building for Windows Store

Many contribs use forbidden APIs that are mapped to valid APIs in the
winstorecompat. We make sure they map to these calls with the define and
linking with the matching library.

(cherry picked from commit 8a793922) (rebased)
rebased:
- the code around is slightly different

contrib/src/main.mak

@@ -164,6 +164,11 @@ EXTRA_LDFLAGS += -m32
 endif
 endif
 
+ifdef HAVE_WINSTORE
+EXTRA_CFLAGS += -DWINSTORECOMPAT
+EXTRA_LDFLAGS += -lwinstorecompat
+endif
+
 ifneq ($(findstring clang, $(shell $(CC) --version)),)
 HAVE_CLANG := 1
 endif