compilers: Fix output ext while compile-only on MSVC
compilers: Fix output ext while compile-only on MSVC

When doing a compile-only self.compile() check, cl.exe expects an output
file of type *.obj, and passing it `output.exe` makes it write the
compiled object to `output.exe.obj`. Detect when we're doing
a compily-only check and change the suffix ourselves.

This is fine most of the time, but fails when you need to inspect the
compiled file manually.

Also store stdout/stderr on the returned object.

mesonbuild/meson,fmuellner/meson,ernestask/meson,QuLogic/meson,wberrier/meson,fmuellner/meson,MathieuDuponchelle/meson,becm/meson,wberrier/meson,wberrier/meson,mesonbuild/meson,jeandet/meson,ernestask/meson,jpakkane/meson,ernestask/meson,QuLogic/meson,thiblahute/meson,becm/meson,pexip/meson,aaronp24/meson,MathieuDuponchelle/meson,rhd/meson,ernestask/meson,jpakkane/meson,jeandet/meson,wberrier/meson,wberrier/meson,aaronp24/meson,jeandet/meson,mesonbuild/meson,jeandet/meson,jeandet/meson,QuLogic/meson,ernestask/meson,ernestask/meson,trhd/meson,trhd/meson,jpakkane/meson,becm/meson,trhd/meson,QuLogic/meson,pexip/meson,jeandet/meson,wberrier/meson,jpakkane/meson,thiblahute/meson,becm/meson,mesonbuild/meson,MathieuDuponchelle/meson,mesonbuild/meson,becm/meson,aaronp24/meson,pexip/meson,fmuellner/meson,thiblahute/meson,jeandet/meson,jpakkane/meson,thiblahute/meson,becm/meson,jpakkane/meson,pexip/meson,rhd/meson,jeandet/meson,fmuellner/meson,QuLogic/meson,thiblahute/meson,ernestask/meson,thiblahute/meson,fmuellner/meson,MathieuDuponchelle/meson,pexip/meson,becm/meson,QuLogic/meson,rhd/meson,pexip/meson,trhd/meson,jpakkane/meson,aaronp24/meson,QuLogic/meson,pexip/meson,MathieuDuponchelle/meson,aaronp24/meson,fmuellner/meson,ernestask/meson,rhd/meson,thiblahute/meson,mesonbuild/meson,rhd/meson,jpakkane/meson,becm/meson,becm/meson,mesonbuild/meson,wberrier/meson,pexip/meson,jpakkane/meson,pexip/meson,thiblahute/meson,mesonbuild/meson,MathieuDuponchelle/meson,aaronp24/meson,trhd/meson,fmuellner/meson,jeandet/meson,trhd/meson,mesonbuild/meson,trhd/meson,trhd/meson,fmuellner/meson,aaronp24/meson,wberrier/meson,MathieuDuponchelle/meson,rhd/meson,rhd/meson,MathieuDuponchelle/meson,becm/meson,fmuellner/meson,MathieuDuponchelle/meson,aaronp24/meson,rhd/meson,trhd/meson,thiblahute/meson,QuLogic/meson,aaronp24/meson,ernestask/meson,QuLogic/meson,mesonbuild/meson,pexip/meson