[clang/test] Fix a flaky unittest on windows

[etienneb]

Summary

The append operator on a shell command for quick command-line is
causing trouble on windows. [NFC]
The easiest way to fix them is to avoid using them.

This patch is an attempt to fix this broken build bot:

clang-x86-win2008-selfhost

http://lab.llvm.org:8011/builders/clang-x86-win2008-selfhost/builds/9523

[rnk]

Thanks! lgtm

cfe/trunk/test/Modules/no-stale-modtime.m

 // Ensure that when rebuilding a module we don't save its old modtime when
 // building modules that depend on it.
 
 // RUN: rm -rf %t
 // RUN: mkdir -p %t
 // This could be replaced by diamond_*, except we want to modify the top header
 // RUN: echo '@import l; @import r;' > %t/b.h
 // RUN: echo '@import t; // fromt l' > %t/l.h
 // RUN: echo '@import t; // fromt r' > %t/r.h
-// RUN: echo '// top' > %t/t.h
-// RUN: echo 'module b { header "b.h" } module l { header "l.h" }' > %t/module.map
-// RUN: echo 'module r { header "r.h" } module t { header "t.h" }' >> %t/module.map
+
+// RUN: echo '// top' > %t/t.h-1
+// RUN: cat %t/t.h-1 > %t/t.h
+
+// RUN: echo 'module b { header "b.h" } module l { header "l.h" }' > %t/module.map-1
+// RUN: echo 'module r { header "r.h" } module t { header "t.h" }' > %t/module.map-2
+// RUN: cat %t/module.map-1 %t/module.map-2 > %t/module.map
 
 // RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fdisable-module-hash \
 // RUN:     -I %t -fsyntax-only %s -Rmodule-build 2>&1 \
 // RUN: | FileCheck -check-prefix=REBUILD-ALL %s
 // RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fdisable-module-hash \
 // RUN:     -I %t -fsyntax-only %s -Rmodule-build -verify
 
 // Add an identifier to ensure everything depending on t is out of date
-// RUN: echo 'extern int a;' >> %t/t.h
+// RUN: echo 'extern int a;' > %t/t.h-2
+// RUN: cat %t/t.h-1 %t/t.h-2 > %t/t.h
+
 // RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fdisable-module-hash \
 // RUN:     -I %t -fsyntax-only %s -Rmodule-build 2>&1 \
 // RUN: | FileCheck -check-prefix=REBUILD-ALL %s
 // RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fdisable-module-hash \
 // RUN:     -I %t -fsyntax-only %s -Rmodule-build -verify
 
 // REBUILD-ALL: building module 'b'
 // REBUILD-ALL: building module 'l'
 // REBUILD-ALL: building module 't'
 // REBUILD-ALL: building module 'r'
 
 // Use -verify when expecting no modules to be rebuilt.
 // expected-no-diagnostics
 
 @import b;