Check for exported weak symbols

Ouch, all our C++ inline functions are being exported (weakly) already.
Fix coming.

src/check-internal-symbols.sh

@@ -14,12 +14,18 @@ else
 	exit 77
 fi
 
+if which c++filt 2>/dev/null >/dev/null; then
+	cplusplusfilt=c++filt
+else
+	cplusplusfilt=cat
+fi
+
 tested=false
 for suffix in so; do
 	so=.libs/libharfbuzz.$suffix
 	if test -f "$so"; then
 		echo "Checking that we are not exposing internal symbols"
-		if nm $so | grep ' T ' | grep -v ' T _fini\>\| T _init\>\| T hb_'; then
+		if nm $so | grep ' [TW] ' | $cplusplusfilt | grep -v ' T _fini\>\| T _init\>\| T hb_'; then
 			echo "Ouch, internal symbols exposed"
 			stat=1
 		fi