expat: fix WASM build

it fails with
/home/tdf/lode/jenkins/workspace/lo_gerrit/tb/build_master/workdir/UnpackedTarball/expat/lib/random_getrandom.c:78:14: error: call to undeclared function 'syscall'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   78 |         (int)syscall(SYS_getrandom, currentTarget, bytesToWrite,
      |              ^
/home/tdf/lode/jenkins/workspace/lo_gerrit/tb/build_master/workdir/UnpackedTarball/expat/lib/random_getrandom.c:78:22: error: use of undeclared identifier 'SYS_getrandom'
   78 |         (int)syscall(SYS_getrandom, currentTarget, bytesToWrite,
      |                      ^~~~~~~~~~~~~
2 errors generated.

Change-Id: I994f10533315c055e1da07fad982a6100e1856ef
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/204732
Tested-by: Jenkins
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>

external/expat/ExternalProject_expat.mk

@@ -18,6 +18,7 @@ $(call gb_ExternalProject_get_state_target,expat,configure) :
 	$(call gb_ExternalProject_run,configure,\
 		$(gb_RUN_CONFIGURE) ./configure --without-docbook --without-getentropy \
 				--without-arc4random --without-arc4random-buf \
+				--without-getrandom --without-sys-getrandom \
 			$(gb_CONFIGURE_PLATFORMS) \
 			$(if $(CROSS_COMPILING),$(if $(filter INTEL ARM,$(CPUNAME)),ac_cv_c_bigendian=no)) \
 	,,expat_configure.log)

external/expat/StaticLibrary_expat.mk

@@ -42,18 +42,13 @@ $(eval $(call gb_StaticLibrary_add_defs,expat,\
 ))
 endif
 
-ifeq ($(OS),MACOSX)
-$(eval $(call gb_StaticLibrary_add_generated_cobjects,expat,\
-	UnpackedTarball/expat/lib/random_dev_urandom \
-))
-else ifeq ($(OS),WNT)
+ifeq ($(OS),WNT)
 $(eval $(call gb_StaticLibrary_add_generated_cobjects,expat,\
 	UnpackedTarball/expat/lib/random_rand_s \
 ))
 else
 $(eval $(call gb_StaticLibrary_add_generated_cobjects,expat,\
 	UnpackedTarball/expat/lib/random_dev_urandom \
-	UnpackedTarball/expat/lib/random_getrandom \
 ))
 endif