--- a/libcxx/lib/buildit
+++ b/libcxx/lib/buildit
@@ -99,6 +99,13 @@
     ;;
 esac
 
+#Debian build flags
+CPPFLAGS="`dpkg-buildflags --get CPPFLAGS` $CPPFLAGS"
+CFLAGS="`dpkg-buildflags --get CFLAGS` $CFLAGS"
+CXXFLAGS="`dpkg-buildflags --get CXXFLAGS` $CXXFLAGS"
+LDFLAGS="`dpkg-buildflags --get LDFLAGS` $LDFLAGS"
+EXTRA_FLAGS="$CPPFLAGS $CFLAGS $CXXFLAGS $LDFLAGS $EXTRA_FLAGS"
+
 if [ -z $RC_XBS ]
 then
     rm -f libc++.1.$SOEXT*
--- a/libcxxabi/lib/buildit
+++ b/libcxxabi/lib/buildit
@@ -74,6 +74,13 @@
     ;;
 esac
 
+#Debian build flags
+CPPFLAGS="`dpkg-buildflags --get CPPFLAGS` $CPPFLAGS"
+CFLAGS="`dpkg-buildflags --get CFLAGS` $CFLAGS"
+CXXFLAGS="`dpkg-buildflags --get CXXFLAGS` $CXXFLAGS"
+LDFLAGS="`dpkg-buildflags --get LDFLAGS` $LDFLAGS"
+EXTRA_FLAGS="$CPPFLAGS $CFLAGS $CXXFLAGS $LDFLAGS $EXTRA_FLAGS"
+
 if [ -z $RC_XBS ]
 then
     rm -f libc++abi.1.$SOEXT*