Fixed the use of HOST_NSPR_MDCPUCFG so that the build doesn't break if it is not defined.

config/rules.mk

@@ -80,8 +80,8 @@ endif
 ifdef INTERNAL_TOOLS
 CC=$(HOST_CC)
 CXX=$(HOST_CXX)
-CFLAGS=$(HOST_CFLAGS) -I$(DIST)/include $(NSPR_CFLAGS) -DMDCPUCFG=$(HOST_NSPR_MDCPUCFG)
-CXXFLAGS=$(HOST_CXXFLAGS) -I$(DIST)/include $(NSPR_CFLAGS) -DMDCPUCFG=$(HOST_NSPR_MDCPUCFG)
+CFLAGS=$(HOST_CFLAGS) -I$(DIST)/include $(NSPR_CFLAGS)
+CXXFLAGS=$(HOST_CXXFLAGS) -I$(DIST)/include $(NSPR_CFLAGS)
 RANLIB=$(HOST_RANLIB)
 endif
 

xpcom/typelib/xpidl/Makefile.in

@@ -43,6 +43,10 @@ include $(topsrcdir)/config/rules.mk
 
 CFLAGS += $(LIBIDL_CFLAGS)
 
+ifdef HOST_NSPR_MDCPUCFG
+CFLAGS += -DMDCPUCFG=$(HOST_NSPR_MDCPUCFG)
+endif
+
 # Tell the $(PROGRAM) target that we need to be recompiled when libxpt changes.
 EXTRA_DEPS = $(wildcard $(DIST)/lib/libxpt.*)
 

xpcom/typelib/xpt/src/Makefile.in

@@ -45,3 +45,8 @@ override NO_STATIC_LIB=
 export:: libs
 
 include $(topsrcdir)/config/rules.mk
+
+ifdef HOST_NSPR_MDCPUCFG
+CFLAGS += -DMDCPUCFG=$(HOST_NSPR_MDCPUCFG)
+endif
+

xpcom/typelib/xpt/tools/Makefile.in

@@ -43,3 +43,6 @@ INTERNAL_TOOLS = 1
 
 include $(topsrcdir)/config/rules.mk
 
+ifdef HOST_NSPR_MDCPUCFG
+CFLAGS += -DMDCPUCFG=$(HOST_NSPR_MDCPUCFG)
+endif