Merge remote-tracking branch 'origin/master' into llvm11

The changes to install_files.h needed to put into src/libcxx.zig

src/zig_llvm.cpp

@@ -930,7 +930,7 @@ class MyOStream: public raw_ostream {
 };
 
 bool ZigLLVMWriteImportLibrary(const char *def_path, const ZigLLVM_ArchType arch,
-                               const char *output_lib_path, const bool kill_at)
+                               const char *output_lib_path, bool kill_at)
 {
     COFF::MachineTypes machine = COFF::IMAGE_FILE_MACHINE_UNKNOWN;