configure: consistently pass CFLAGS/CXXFLAGS/LDFLAGS to meson

Environment variables like CFLAGS are easy to accidentally change.  Meson
warns if that happens, but in a project with a lot of configuration that
is easy to lose.  It is also surprising behavior since meson caches -D
options and remembers those on reconfiguration (which we rely on,
since configure options become -D options).

By placing the user-provided CFLAGS, CXXFLAGS and LDFLAGS in the
cross file, we at least get consistent behavior.  These environment
variables are still ugly and not really recommended, but there are
distros that rely on them.  For the gory details, refer to
mesonbuild/meson#4664.

Tested-by: Richard Henderson <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

configure

@@ -7130,24 +7130,29 @@ echo "export PYTHON='$python'" >> "$iotests_common_env"
 if test "$skip_meson" = no; then
 cross="config-meson.cross.new"
 meson_quote() {
-    echo "['$(echo $* | sed "s/ /','/g")']"
+    echo "'$(echo $* | sed "s/ /','/g")'"
 }
 
 echo "# Automatically generated by configure - do not modify" > $cross
 echo "[properties]" >> $cross
 test -z "$cxx" && echo "link_language = 'c'" >> $cross
+echo "[built-in options]" >> $cross
+echo "c_args = [${CFLAGS:+$(meson_quote $CFLAGS)}]" >> $cross
+echo "cpp_args = [${CXXFLAGS:+$(meson_quote $CXXFLAGS)}]" >> $cross
+echo "c_link_args = [${LDFLAGS:+$(meson_quote $LDFLAGS)}]" >> $cross
+echo "cpp_link_args = [${LDFLAGS:+$(meson_quote $LDFLAGS)}]" >> $cross
 echo "[binaries]" >> $cross
-echo "c = $(meson_quote $cc)" >> $cross
-test -n "$cxx" && echo "cpp = $(meson_quote $cxx)" >> $cross
-echo "ar = $(meson_quote $ar)" >> $cross
-echo "nm = $(meson_quote $nm)" >> $cross
-echo "pkgconfig = $(meson_quote $pkg_config_exe)" >> $cross
-echo "ranlib = $(meson_quote $ranlib)" >> $cross
+echo "c = [$(meson_quote $cc)]" >> $cross
+test -n "$cxx" && echo "cpp = [$(meson_quote $cxx)]" >> $cross
+echo "ar = [$(meson_quote $ar)]" >> $cross
+echo "nm = [$(meson_quote $nm)]" >> $cross
+echo "pkgconfig = [$(meson_quote $pkg_config_exe)]" >> $cross
+echo "ranlib = [$(meson_quote $ranlib)]" >> $cross
 if has $sdl2_config; then
-  echo "sdl2-config = $(meson_quote $sdl2_config)" >> $cross
+  echo "sdl2-config = [$(meson_quote $sdl2_config)]" >> $cross
 fi
-echo "strip = $(meson_quote $strip)" >> $cross
-echo "windres = $(meson_quote $windres)" >> $cross
+echo "strip = [$(meson_quote $strip)]" >> $cross
+echo "windres = [$(meson_quote $windres)]" >> $cross
 if test -n "$cross_prefix"; then
     cross_arg="--cross-file config-meson.cross"
     echo "[host_machine]" >> $cross

meson.build

@@ -1771,8 +1771,18 @@ if targetos == 'darwin'
   summary_info += {'Objective-C compiler': meson.get_compiler('objc').cmd_array()[0]}
 endif
 summary_info += {'ARFLAGS':           config_host['ARFLAGS']}
-summary_info += {'CFLAGS':            '-O' + get_option('optimization')
-                                           + (get_option('debug') ? ' -g' : '')}
+summary_info += {'CFLAGS':            ' '.join(get_option('c_args')
+                                               + ['-O' + get_option('optimization')]
+                                               + (get_option('debug') ? ['-g'] : []))}
+if link_language == 'cpp'
+  summary_info += {'CXXFLAGS':        ' '.join(get_option('cpp_args')
+                                               + ['-O' + get_option('optimization')]
+                                               + (get_option('debug') ? ['-g'] : []))}
+endif
+link_args = get_option(link_language + '_link_args')
+if link_args.length() > 0
+  summary_info += {'LDFLAGS':         ' '.join(link_args)}
+endif
 summary_info += {'QEMU_CFLAGS':       config_host['QEMU_CFLAGS']}
 summary_info += {'QEMU_LDFLAGS':      config_host['QEMU_LDFLAGS']}
 summary_info += {'make':              config_host['MAKE']}