--- a/Make.Rules
+++ b/Make.Rules
@@ -47,25 +47,18 @@
 KERNEL_HEADERS := $(topdir)/libcap/include
 IPATH += -fPIC -I$(topdir)/libcap/include -I$(KERNEL_HEADERS)
 
-CC := gcc
-CFLAGS := -O2
-BUILD_CC := $(CC)
-BUILD_CFLAGS := $(CFLAGS) $(IPATH)
-AR := ar
-RANLIB := ranlib
 DEBUG = -g #-DDEBUG
 WARNINGS=-Wall -Wwrite-strings \
         -Wpointer-arith -Wcast-qual -Wcast-align \
         -Wstrict-prototypes -Wmissing-prototypes \
         -Wnested-externs -Winline -Wshadow
 LD=$(CC) -Wl,-x -shared
-LDFLAGS := #-g
 
-SYSTEM_HEADERS = /usr/include
+SYSTEM_HEADERS ?= /usr/include
 INCS=$(topdir)/libcap/include/sys/capability.h
 LDFLAGS += -L$(topdir)/libcap
 CFLAGS += -Dlinux $(WARNINGS) $(DEBUG)
-PAM_CAP := $(shell if [ -f /usr/include/security/pam_modules.h ]; then echo yes ; else echo no ; fi)
+PAM_CAP := $(shell if [ -f $(SYSTEM_HEADERS)/security/pam_modules.h ]; then echo yes ; else echo no ; fi)
 INDENT := $(shell if [ -n "$(which indent 2>/dev/null)" ]; then echo "| indent -kr" ; fi)
 DYNAMIC := $(shell if [ ! -d "$(topdir)/.git" ]; then echo yes; fi)
 LIBATTR := yes