contrib:gmp: do not try to detect assembler format when assembler is disabled

contrib/src/gmp/gmp-fix-asm-detection.patch

+--- gmp/configure.ac.asm	2018-06-25 13:50:38.561396100 +0200
++++ gmp/configure.ac	2018-06-25 14:02:43.731673800 +0200
+@@ -3592,7 +3592,7 @@ if test $found_asm = yes; then
+ fi
+ 
+ # Only do the GMP_ASM checks if there's a .S or .asm wanting them.
+-if test $found_asm = no && test $found_S = no; then
++if test $found_asm = no || test $enable_assembly = no ; then
+   gmp_asm_syntax_testing=no
+ fi
+ 

contrib/src/gmp/rules.mak

@@ -34,6 +34,7 @@ gmp: gmp-$(GMP_VERSION).tar.bz2 .sum-gmp
 	$(UNPACK)
 	$(APPLY) $(SRC)/gmp/ppc64.patch
 	$(APPLY) $(SRC)/gmp/win-arm64.patch
+	$(APPLY) $(SRC)/gmp/gmp-fix-asm-detection.patch
 	$(MOVE)
 
 # GMP requires either GPLv2 or LGPLv3