stage2: enable building libssp

This was disabled when self-hosted was less capable; now it is time to
enable it.

See related issue #7265

Author: andrewrk

src/Compilation.zig

@@ -1932,7 +1932,7 @@ pub fn create(gpa: Allocator, options: InitOptions) !*Compilation {
         const capable_of_building_compiler_rt = build_options.have_llvm;
 
         const capable_of_building_zig_libc = build_options.have_llvm;
-        const capable_of_building_ssp = comp.bin_file.options.use_stage1;
+        const capable_of_building_ssp = build_options.have_llvm;
 
         if (comp.bin_file.options.include_compiler_rt and capable_of_building_compiler_rt) {
             if (is_exe_or_dyn_lib) {