Driver test: remove `REQUIRES: x86-registered-target` and set `--sysroot=""` to support clang with `DEFAULT_SYSROOT`.

[MaggieYi]

Summary

When testing clang that has been compiled with -DDEFAULT_SYSROOT set to some path, ps4-ps5-header-search.c would fail.

The test needs to be updated.

1. Remove unnecessary REQUIRES: x86-registered-target.
2. Override sysroot to be empty string for the test to succeed when clang is configured with DEFAULT_SYSROOT.

[wristow]

LGTM

[probinson]

Closing this for @MaggieYi the commit message didn't cite the Phabricator review.
https://github.com/llvm/llvm-project/commit/5de4d97a00b2a5d710892e96d77810784fd2cd5c

clang/test/Driver/ps4-ps5-header-search.c

-// REQUIRES: x86-registered-target
-
 /// PS4 and PS5 use the same SDK layout, so use the same tree for both.
-// 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
-// RUN: env SCE_PROSPERO_SDK_DIR=%S/Inputs/scei-ps4_tree %clang -target x86_64-sie-ps5 -E -v %s 2>&1 | FileCheck %s --check-prefix=ENVPS4
+// RUN: env SCE_ORBIS_SDK_DIR=%S/Inputs/scei-ps4_tree %clang -target x86_64-scei-ps4 --sysroot="" -E -v %s 2>&1 | FileCheck %s --check-prefix=ENVPS4
+// RUN: env SCE_PROSPERO_SDK_DIR=%S/Inputs/scei-ps4_tree %clang -target x86_64-sie-ps5 --sysroot="" -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
 // RUN: %clang -isysroot %S/Inputs/scei-ps4_tree -target x86_64-sie-ps5 -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