[PS4] Fix header search list

A missing "break" in the initial implementation had us adding a
spurious "/usr/include" to the header search list. Later someone
introduced LLVM_FALLTHROUGH to prevent a warning.  Replace this with
the correct "break" and make sure the extra directory isn't added to
the PS4 header search list.

clang/lib/Lex/InitHeaderSearch.cpp

@@ -372,7 +372,7 @@ void InitHeaderSearch::AddDefaultCIncludePaths(const llvm::Triple &triple,
     AddPath(BaseSDKPath + "/target/include", System, false);
     if (triple.isPS4())
       AddPath(BaseSDKPath + "/target/include_common", System, false);
-    LLVM_FALLTHROUGH;
+    break;
   }
   default:
     AddPath("/usr/include", ExternCSystem, false);

clang/test/Driver/ps4-header-search.c

@@ -3,8 +3,10 @@
 // RUN: env SCE_ORBIS_SDK_DIR=%S/Inputs/scei-ps4_tree %clang -target x86_64-scei-ps4 -E -v %s 2>&1 | FileCheck %s --check-prefix=ENVPS4
 // ENVPS4: Inputs/scei-ps4_tree/target/include{{$}}
 // ENVPS4: Inputs/scei-ps4_tree/target/include_common{{$}}
+// ENVPS4-NOT: /usr/include
 
 // RUN: %clang -isysroot %S/Inputs/scei-ps4_tree -target x86_64-scei-ps4 -E -v %s 2>&1 | FileCheck %s --check-prefix=SYSROOTPS4
 // SYSROOTPS4: "{{[^"]*}}clang{{[^"]*}}"
 // SYSROOTPS4: Inputs/scei-ps4_tree/target/include{{$}}
 // SYSROOTPS4: Inputs/scei-ps4_tree/target/include_common{{$}}
+// SYSROOTPS4-NOT: /usr/include