configure: Pass filtered QEMU_OBJCFLAGS to meson

Filter unsupported Objective-C options, to avoid
'unknown-warning-option' warnings when using Clang:

  [34/373] Compiling Objective-C object libcommon.fa.p/audio_coreaudio.m.o
  warning: unknown warning option '-Wold-style-declaration'; did you mean '-Wout-of-line-declaration'? [-Wunknown-warning-option]
  warning: unknown warning option '-Wimplicit-fallthrough=2'; did you mean '-Wimplicit-fallthrough'? [-Wunknown-warning-option]
  2 warnings generated.

Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Tested-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

configure

@@ -77,6 +77,7 @@ TMPB="qemu-conf"
 TMPC="${TMPDIR1}/${TMPB}.c"
 TMPO="${TMPDIR1}/${TMPB}.o"
 TMPCXX="${TMPDIR1}/${TMPB}.cxx"
+TMPM="${TMPDIR1}/${TMPB}.m"
 TMPE="${TMPDIR1}/${TMPB}.exe"
 
 rm -f config.log
@@ -148,6 +149,10 @@ do_cxx() {
     do_compiler "$cxx" $CPU_CFLAGS "$@"
 }
 
+do_objc() {
+    do_compiler "$objcc" $CPU_CFLAGS "$@"
+}
+
 # Append $2 to the variable named $1, with space separation
 add_to() {
     eval $1=\${$1:+\"\$$1 \"}\$2
@@ -1445,10 +1450,27 @@ cc_has_warning_flag() {
     compile_prog "-Werror $optflag" ""
 }
 
+objcc_has_warning_flag() {
+    cat > $TMPM <<EOF
+int main(void) { return 0; }
+EOF
+
+    # Use the positive sense of the flag when testing for -Wno-wombat
+    # support (gcc will happily accept the -Wno- form of unknown
+    # warning options).
+    optflag="$(echo $1 | sed -e 's/^-Wno-/-W/')"
+    do_objc -Werror $optflag \
+      $OBJCFLAGS $EXTRA_OBJCFLAGS $CONFIGURE_OBJCFLAGS $QEMU_OBJCFLAGS \
+      -o $TMPE $TMPM $QEMU_LDFLAGS
+}
+
 for flag in $gcc_flags; do
     if cc_has_warning_flag $flag ; then
         QEMU_CFLAGS="$QEMU_CFLAGS $flag"
     fi
+    if objcc_has_warning_flag $flag ; then
+        QEMU_OBJCFLAGS="$QEMU_OBJCFLAGS $flag"
+    fi
 done
 
 if test "$stack_protector" != "no"; then
@@ -2990,6 +3012,7 @@ echo "LD=$ld" >> $config_host_mak
 echo "CFLAGS_NOPIE=$CFLAGS_NOPIE" >> $config_host_mak
 echo "QEMU_CFLAGS=$QEMU_CFLAGS" >> $config_host_mak
 echo "QEMU_CXXFLAGS=$QEMU_CXXFLAGS" >> $config_host_mak
+echo "QEMU_OBJCFLAGS=$QEMU_OBJCFLAGS" >> $config_host_mak
 echo "GLIB_CFLAGS=$glib_cflags" >> $config_host_mak
 echo "GLIB_LIBS=$glib_libs" >> $config_host_mak
 echo "GLIB_VERSION=$(pkg-config --modversion glib-2.0)" >> $config_host_mak

meson.build

@@ -173,11 +173,13 @@ endif
 
 qemu_cflags = config_host['QEMU_CFLAGS'].split()
 qemu_cxxflags = config_host['QEMU_CXXFLAGS'].split()
+qemu_objcflags = config_host['QEMU_OBJCFLAGS'].split()
 qemu_ldflags = config_host['QEMU_LDFLAGS'].split()
 
 if get_option('gprof')
   qemu_cflags += ['-p']
   qemu_cxxflags += ['-p']
+  qemu_objcflags += ['-p']
   qemu_ldflags += ['-p']
 endif
 
@@ -216,8 +218,9 @@ if get_option('fuzzing')
   endif
 endif
 
-add_global_arguments(qemu_cflags, native: false, language: ['c', 'objc'])
+add_global_arguments(qemu_cflags, native: false, language: ['c'])
 add_global_arguments(qemu_cxxflags, native: false, language: ['cpp'])
+add_global_arguments(qemu_objcflags, native: false, language: ['objc'])
 add_global_link_arguments(qemu_ldflags, native: false, language: ['c', 'cpp', 'objc'])
 
 if targetos == 'linux'
@@ -3481,6 +3484,7 @@ if link_args.length() > 0
 endif
 summary_info += {'QEMU_CFLAGS':       config_host['QEMU_CFLAGS']}
 summary_info += {'QEMU_CXXFLAGS':     config_host['QEMU_CXXFLAGS']}
+summary_info += {'QEMU_OBJCFLAGS':    config_host['QEMU_OBJCFLAGS']}
 summary_info += {'QEMU_LDFLAGS':      config_host['QEMU_LDFLAGS']}
 summary_info += {'profiler':          get_option('profiler')}
 summary_info += {'link-time optimization (LTO)': get_option('b_lto')}