Work around clang-cl issue with __int128

(see external/libtommath/clang-cl.patch for details)

Change-Id: Ice2e1b3e3c5944b3ae72365981679c1effdcfdbd
Reviewed-on: https://gerrit.libreoffice.org/45342
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

external/libtommath/UnpackedTarball_libtommath.mk

@@ -15,6 +15,7 @@ $(eval $(call gb_UnpackedTarball_set_patchlevel,libtommath,0))
 
 $(eval $(call gb_UnpackedTarball_add_patches,libtommath,\
 	external/libtommath/libtommath-msvc.patch \
+	external/libtommath/clang-cl.patch \
 ))
 
 # vim: set noet sw=4 ts=4:

external/libtommath/clang-cl.patch

@@ -0,0 +1,16 @@
+--- tommath.h
++++ tommath.h
+@@ -15,6 +15,13 @@
+ #ifndef BN_H_
+ #define BN_H_
+ 
++// Work around clang-cl issue when mp_word is a typedef for unsigned __int128, see
++// <https://bugs.llvm.org/show_bug.cgi?id=25305> "Clang-cl generates a call to an undefined symbol
++// _udivti3":
++#if defined _WIN32 && defined __clang__
++#define MP_8BIT
++#endif
++
+ #include <stdio.h>
+ #include <stdlib.h>
+ #include <stdint.h>