build: Properly select the right system wrappers

This is needed for windows build to be usable.

https://bugs.freedesktop.org/show_bug.cgi?id=96754

configure.ac

@@ -53,11 +53,13 @@ AS_CASE(["${host}"],
         [
          OS_CFLAGS="-DWEBRTC_ANDROID -DWEBRTC_LINUX"
          PLATFORM_CFLAGS="-DWEBRTC_POSIX"
+         HAVE_POSIX=1
         ],
     [*-*linux*],
         [
          OS_CFLAGS="-DWEBRTC_LINUX"
          PLATFORM_CFLAGS="-DWEBRTC_POSIX"
+         HAVE_POSIX=1
         ],
     [*-*darwin*],
         [
@@ -65,13 +67,17 @@ AS_CASE(["${host}"],
              [OS_FLAGS="-DWEBRTC_MAC -DWEBRTC_IOS"],
              [OS_FLAGS="-DWEBRTC_MAC"])
          PLATFORM_CFLAGS="-DWEBRTC_POSIX"
+         HAVE_POSIX=1
         ],
     [*-mingw32*],
         [
          PLATFORM_CFLAGS="-DWEBRTC_WIN -U__STRICT_ANSI__"
+         HAVE_WIN=1
         ]
 )
 AC_SUBST(PLATFORM_CFLAGS)
+AM_CONDITIONAL(HAVE_POSIX, [test "x${HAVE_POSIX}" = "x1"])
+AM_CONDITIONAL(HAVE_WIN, [test "x${HAVE_WIN}" = "x1"])
 
 AS_CASE(["${host_cpu}"],
     [i?86|x86_64],

webrtc/system_wrappers/Makefile.am

@@ -42,13 +42,21 @@ libsystem_wrappers_la_SOURCES = include/aligned_malloc.h \
 				source/trace_impl.h \
 				source/trace_posix.h \
 				source/trace_win.h
-# This assumes that we want the POSIX implementation -- should eventually be
-# converted to a conditional to include Windows support
+if HAVE_POSIX
 libsystem_wrappers_la_SOURCES += source/critical_section_posix.cc \
 				 source/event_timer_posix.cc \
 				 source/rw_lock_posix.cc \
 				 source/thread_posix.cc \
 				 source/trace_posix.cc
+endif
+if HAVE_WIN
+libsystem_wrappers_la_SOURCES += source/critical_section_win.cc \
+				 source/event_timer_win.cc \
+				 source/rw_lock_win.cc \
+				 source/rw_lock_generic.cc \
+				 source/thread_win.cc \
+				 source/trace_win.cc
+endif
 libsystem_wrappers_la_CXXFLAGS = $(AM_CXXFLAGS) $(COMMON_CXXFLAGS)
 
 EXTRA_DIST = BUILD.gn \