force the use of gcc on cygwin for concat-deps.c

bootstrap

@@ -76,8 +76,12 @@ fi
 
 # build concat-deps
 echo "building concat-deps"
-$CC_FOR_BUILD -O2 "$SOLARENV/bin/concat-deps.c" -o "$SOLARENV/bin/concat-deps" || exit
-
+if [ "$COM_FOR_BUILD" = "MSC" ] ; then
+    # on cygwin force the use of gcc
+    gcc -O2 "$SOLARENV/bin/concat-deps.c" -o "$SOLARENV/bin/concat-deps" || exit
+else
+    $CC_FOR_BUILD -O2 "$SOLARENV/bin/concat-deps.c" -o "$SOLARENV/bin/concat-deps" || exit
+fi
 #make sure build.pl is executable
 
 chmod +x "$SRC_ROOT/solenv/bin/build.pl"