[freetype2] enable fsanitize=function

Bug: https://fxbug.dev/42078767
Change-Id: Idc962668685b060a4b5e8dce74f4b7be0e57c105
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/freetype2/+/1189312
Reviewed-by: Gulfem Savrun Yeniceri <gulfem@google.com>
Reviewed-by: Daniel Thornburgh <dthorn@google.com>

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index db0ea6c..44915e8 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -28,19 +28,13 @@
 
 config("freetype_config") {
   include_dirs = [ "include" ]
-  cflags = [ "-Wno-macro-redefined" ]
-
-  # TODO(fxbug.dev/42078767): freetype2 has a lot of instances of this type of
-  # UB. We should come back and fix these. Disabling this check here though
-  # doesn't change anything since it wasn't until recently that this check was
-  # extended to cover C, so these bugs were already here.
-  cflags_c = [ "-fno-sanitize=function" ]
 }
 
 config("freetype_warnings") {
   cflags = [
     "-Wno-conversion",
     "-Wno-implicit-fallthrough",
+    "-Wno-macro-redefined",
     "-Wno-unused-function",
     "-Wno-unused-variable",
   ]