compilers: Reduce sizes of MSVC linked binaries

- For optimization=s add /O1: Use Maximum Optimization (Favor Size),
  and remove /Os as it's implied by /O1.
- Because we add /O1, this implies /Gy, i.e. Function-Level Linking, so
  unused code can be omitted.
- Add /Gw: Optimize Global Data, so unused data can be omitted.

With buildtype=minsize on x86 this reduces the size of a statically
linked Vala compiler binary from 5 MB down to just 1.87 MB.

1 files changed, 4 insertions, 1 deletions

diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index 3599a99..436f699 100644
--- a/mesonbuild/compilers/c.py
+++ b/mesonbuild/compilers/c.py
@@ -1247,7 +1247,10 @@ class VisualStudioCCompiler(CCompiler):
         return ['/MDd']
 
     def get_buildtype_args(self, buildtype):
-        return compilers.msvc_buildtype_args[buildtype]
+        args = compilers.msvc_buildtype_args[buildtype]
+        if version_compare(self.version, '<18.0'):
+            args = [arg for arg in args if arg != '/Gw']
+        return args
 
     def get_buildtype_linker_args(self, buildtype):
         return compilers.msvc_buildtype_linker_args[buildtype]