debian: Add mechanism to set C/C++ compiler

debian/rules

@@ -4,10 +4,14 @@
 
 #export DH_VERBOSE=1
 
+FS_CC?=gcc
+FS_CXX?=g++
 FS_CFLAGS?=-ggdb3 -O2
 FS_CPPFLAGS?=
 FS_CXXFLAGS?=$(FS_CFLAGS)
 export PATH?=/usr/lib/ccache:/usr/sbin:/usr/bin:/sbin:/bin
+export CC=$(FS_CC)
+export CXX=$(FS_CXX)
 export CFLAGS=$(FS_CFLAGS)
 export CPPFLAGS=$(FS_CPPFLAGS)
 export CXXFLAGS=$(FS_CXXFLAGS)
@@ -16,6 +20,8 @@ show_vars= \
 	echo; \
 	echo "Making target $@"; \
 	echo "PATH='$(PATH)'"; \
+	echo "CC='$(CC)'"; \
+	echo "CXX='$(CXX)'"; \
 	echo "CFLAGS='$(CFLAGS)'"; \
 	echo "CXXFLAGS='$(CXXFLAGS)'"; \
 	echo "CCACHE_DIR='$(CCACHE_DIR)'"; \