os_early_win: make compat_layer_env const to avoid GCC writable strings error.
os_early_win: make compat_layer_env const to avoid GCC writable strings error.

GCC is concerned that we'll be writing to the memory of compat_layer_env
after we've assigned a string literal to it.

We won't, but make compat_layer_env const to soothe the compiler.

Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble