explicit ar path

Makefile

@@ -87,7 +87,7 @@ lua53:
 
 milagro:
 	@echo "-- Building milagro (${system})"
-	if ! [ -r ${pwd}/lib/milagro-crypto-c/CMakeCache.txt ]; then cd ${pwd}/lib/milagro-crypto-c && CC=${gcc} AR=/usr/bin/ar RANLIB=/usr/bin/ranlib LD=${ld} cmake . -DCMAKE_C_FLAGS="${cflags}" -DCMAKE_SYSTEM_NAME="${system}" -DCMAKE_AR=${AR} ${milagro_cmake_flags}; fi
+	if ! [ -r ${pwd}/lib/milagro-crypto-c/CMakeCache.txt ]; then cd ${pwd}/lib/milagro-crypto-c && CC=${gcc} LD=${ld} cmake . -DCMAKE_C_FLAGS="${cflags}" -DCMAKE_SYSTEM_NAME="${system}" -DCMAKE_AR=/usr/bin/ar ${milagro_cmake_flags}; fi
 	if ! [ -r ${pwd}/lib/milagro-crypto-c/lib/libamcl_core.a ]; then CC=${gcc} CFLAGS="${cflags}" AR=${ar} RANLIB=${ranlib} LD=${ld} make -C ${pwd}/lib/milagro-crypto-c VERBOSE=1; fi
 
 check-milagro: milagro