Makefile calls imake again but with ignored CC/LD.
Passing only if set rather than use defaults.
--- a/xmkmf.cpp
+++ b/xmkmf.cpp
@@ -56,7 +56,7 @@
     echo "make Makefiles" &&
-    make Makefiles &&
+    make ${CC:+CC="$CC"} ${LD:+LD="$LD"} Makefiles &&
     echo "make includes" &&
-    make includes &&
+    make ${CC:+CC="$CC"} ${LD:+LD="$LD"} includes &&
     echo "make depend" &&
-    make depend
+    make ${CC:+CC="$CC"} ${LD:+LD="$LD"} depend
     ;;