Bustage fix for *nix platforms.

xpcom/tests/Makefile.in

@@ -69,10 +69,13 @@ CPPSRCS = \
   TestQuickReturn.cpp \
   TestArguments.cpp \
   TestUnicodeArguments.cpp \
-  TestBase64.cpp \
   $(STDCPPFLAGS) \
   $(NULL)
 
+ifeq ($(OS_TARGET),WINNT)
+CPPSRCS += TestBase64.cpp
+endif
+
 ifdef WRAP_STL_INCLUDES
 CPPSRCS += TestSTLWrappers.cpp
 endif