don't derive BUILD_CFLAGS from CFLAGS

It's quite common to set some CFLAGS when cross compiling that will not work on
the host. Provide a definition of BUILD_CFLAGS that will not copy CFLAGS by
default.

Signed-off-by: Rolf Eike Beer <[email protected]>
Signed-off-by: Andrew G. Morgan <[email protected]>
diff --git a/Make.Rules b/Make.Rules
index 42f6bef..97328c1 100644
--- a/Make.Rules
+++ b/Make.Rules
@@ -50,9 +50,10 @@
 IPATH += -fPIC -I$(KERNEL_HEADERS) -I$(topdir)/libcap/include
 
 CC := gcc # -std=c99
-CFLAGS := -O2 -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
+DEFINES := -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
+CFLAGS := -O2 $(DEFINES)
 BUILD_CC := $(CC)
-BUILD_CFLAGS := $(CFLAGS) $(IPATH)
+BUILD_CFLAGS := -O2 $(DEFINES) $(IPATH)
 AR := ar
 RANLIB := ranlib
 DEBUG = -g #-DDEBUG