gcc: gcc 6.3.0 fix comparison between pointer and integer

Fix FS#832

/source/build_dir/toolchain-mips_74kc_gcc-6.3.0_musl/gcc-6.3.0/gcc/ubsan.c:
In function 'bool ubsan_use_new_style_p(location_t)':
/source/build_dir/toolchain-mips_74kc_gcc-6.3.0_musl/gcc-6.3.0/gcc/ubsan.c:1474:23:
error: ISO C++ forbids comparison between pointer and integer
[-fpermissive]
       || xloc.file == '\0' || xloc.file[0] == '\xff'
                       ^~~~
make[5]: *** [Makefile:1085: ubsan.o] Error 1

https://www.viva64.com/en/b/0425/#ID0EMGCI

Signed-off-by: Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk>

toolchain/gcc/patches/6.3.0/960-fix-ubsan-defref.patch

@@ -0,0 +1,11 @@
+--- a/gcc/ubsan.c
++++ b/gcc/ubsan.c
+@@ -1471,7 +1471,7 @@ ubsan_use_new_style_p (location_t loc)
+ 
+   expanded_location xloc = expand_location (loc);
+   if (xloc.file == NULL || strncmp (xloc.file, "\1", 2) == 0
+-      || xloc.file == '\0' || xloc.file[0] == '\xff'
++      || xloc.file[0] == '\0' || xloc.file[0] == '\xff'
+       || xloc.file[1] == '\xff')
+     return false;
+