[toplevel] Overhaul detection of target compilers

[DJ Delorie]

> >This breaks newlib cross builds. 
> >  
> I am looking at it.

Try this.  *GCC defaults to *CC's value so it should be safe, but
that's just from a brief review.  Plus, my cross build is working with
this patch ;-)

Index: Makefile.tpl
===================================================================
RCS file: /cvs/src/src/Makefile.tpl,v
retrieving revision 1.143
diff -p -U3 -r1.143 Makefile.tpl
--- Makefile.tpl	8 Aug 2005 09:21:05 -0000	1.143
+++ Makefile.tpl	10 Aug 2005 20:17:31 -0000
@@ -365,7 +365,7 @@ USUAL_AS_FOR_TARGET = ` \
   fi`
 
 CC_FOR_TARGET=$(STAGE_CC_WRAPPER) @CC_FOR_TARGET@ $(FLAGS_FOR_TARGET)
-CONFIGURED_CC_FOR_TARGET=@CONFIGURED_CC_FOR_TARGET@
+CONFIGURED_GCC_FOR_TARGET=@CONFIGURED_GCC_FOR_TARGET@
 USUAL_CC_FOR_TARGET = ` \
   if [ -f $$r/$(HOST_SUBDIR)/gcc/xgcc ] ; then \
     echo $$r/$(HOST_SUBDIR)/gcc/xgcc -B$$r/$(HOST_SUBDIR)/gcc ; \
@@ -373,7 +373,7 @@ USUAL_CC_FOR_TARGET = ` \
     if [ '$(host)' = '$(target)' ] ; then \
       echo $(CC); \
     else \
-      echo $(CONFIGURED_CC_FOR_TARGET) ; \
+      echo $(CONFIGURED_GCC_FOR_TARGET) ; \
     fi; \
   fi`