[PATCH v2] meson.build: default to -gsplit-dwarf for debug info

["Alex Bennée" <alex.bennee@linaro.org>]

This option is supported by both gcc (since 4.7) and clang (since
7.0). Not only does this make the linkers job easier by reducing the
amount of ELF it needs to parse it also reduces the total build size
quite considerably. In my case a default build went from 5.8G to 3.9G.

The --disable-split-debug option allows distros to keep all the info
together for ease of packaging.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

---
v1
  - add --disable/enable-split-debug
  - move to option_cflags
v2
  - removed unneeded []'s
  - fix stray whitespace
---
 meson.build                   | 5 ++++-
 meson_options.txt             | 2 ++
 scripts/meson-buildoptions.sh | 2 ++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index 8d0abe7f12..09e34a6d63 100644
--- a/meson.build
+++ b/meson.build
@@ -4589,7 +4589,10 @@ if have_rust
   summary_info += {'bindgen':         bindgen.full_path()}
   summary_info += {'bindgen version': bindgen.version()}
 endif
-option_cflags = (get_option('debug') ? ['-g'] : [])
+option_cflags = []
+if get_option('debug')
+  option_cflags += get_option('split_debug') ? ['-gsplit-dwarf'] : ['-g']
+endif
 if get_option('optimization') != 'plain'
   option_cflags += ['-O' + get_option('optimization')]
 endif
diff --git a/meson_options.txt b/meson_options.txt
index 59d973bca0..3432123fee 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -362,6 +362,8 @@ option('debug_mutex', type: 'boolean', value: false,
        description: 'mutex debugging support')
 option('debug_stack_usage', type: 'boolean', value: false,
        description: 'measure coroutine stack usage')
+option('split_debug', type: 'boolean', value: true,
+       description: 'split debug info from object files')
 option('qom_cast_debug', type: 'boolean', value: true,
        description: 'cast debugging support')
 option('slirp_smbd', type : 'feature', value : 'auto',
diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
index 3e8e00852b..aca6e68830 100644
--- a/scripts/meson-buildoptions.sh
+++ b/scripts/meson-buildoptions.sh
@@ -504,6 +504,8 @@ _meson_option_parse() {
     --disable-strict-rust-lints) printf "%s" -Dstrict_rust_lints=false ;;
     --enable-strip) printf "%s" -Dstrip=true ;;
     --disable-strip) printf "%s" -Dstrip=false ;;
+    --enable-split-debug) printf "%s" -Dsplit_debug=true ;;
+    --disable-split-debug) printf "%s" -Dsplit_debug=false ;;
     --sysconfdir=*) quote_sh "-Dsysconfdir=$2" ;;
     --enable-tcg) printf "%s" -Dtcg=enabled ;;
     --disable-tcg) printf "%s" -Dtcg=disabled ;;
-- 
2.39.5