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
https://github.com/mesonbuild/meson/issues/4664.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 configure   | 25 +++++++++++++++----------
 meson.build | 14 ++++++++++++--
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/configure b/configure
index a0575f1db1..1129ddb8a1 100755
--- a/configure
+++ b/configure
@@ -7798,24 +7798,29 @@ 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
diff --git a/meson.build b/meson.build
index cb0113ee90..4c73f4093a 100644
--- a/meson.build
+++ b/meson.build
@@ -1471,8 +1471,18 @@ 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']}
-- 
2.26.2