Revert "[lld] Make lld tests use lit internal shell by default"

This reverts commit 714f6b0.

This caused some build failures.
https://lab.llvm.org/buildbot/#/builders/23/builds/13543

Reverting for now until I have a chance to investigate.

Author: boomanaiden154

lld/test/MachO/objc-category-merging-minimal.s

@@ -33,7 +33,7 @@
 
 ############ Test merging skipped due to invalid category name ############
 # Modify __OBJC_$_CATEGORY_MyBaseClass_$_Category01's name to point to L_OBJC_IMAGE_INFO+3
-# RUN: awk '/^__OBJC_\\$_CATEGORY_MyBaseClass_\\$_Category01:/ { print; getline; sub(/^[ \t]*\.quad[ \t]+l_OBJC_CLASS_NAME_$/, "\t.quad\tL_OBJC_IMAGE_INFO+3"); print; next } { print }' merge_cat_minimal.s > merge_cat_minimal_bad_name.s
+# RUN: awk '/^__OBJC_\$_CATEGORY_MyBaseClass_\$_Category01:/ { print; getline; sub(/^[ \t]*\.quad[ \t]+l_OBJC_CLASS_NAME_$/, "\t.quad\tL_OBJC_IMAGE_INFO+3"); print; next } { print }' merge_cat_minimal.s > merge_cat_minimal_bad_name.s
 
 # Assemble the modified source
 # RUN: llvm-mc -filetype=obj -triple=arm64-apple-macos -o merge_cat_minimal_bad_name.o merge_cat_minimal_bad_name.s

lld/test/lit.cfg.py

@@ -16,21 +16,10 @@
 # name: The name of this test suite.
 config.name = "lld"
 
-# TODO: Consolidate the logic for turning on the internal shell by default for all LLVM test suites.
-# See https://github.com/llvm/llvm-project/issues/106636 for more details.
-#
-# We prefer the lit internal shell which provides a better user experience on failures
-# and is faster unless the user explicitly disables it with LIT_USE_INTERNAL_SHELL=0
-# env var.
-use_lit_shell = True
-lit_shell_env = os.environ.get("LIT_USE_INTERNAL_SHELL")
-if lit_shell_env:
-    use_lit_shell = lit.util.pythonize_bool(lit_shell_env)
-
 # testFormat: The test format to use to interpret tests.
 #
 # For now we require '&&' between commands, until they get globally killed and the test runner updated.
-config.test_format = lit.formats.ShTest(execute_external=not use_lit_shell)
+config.test_format = lit.formats.ShTest(not llvm_config.use_lit_shell)
 
 # suffixes: A list of file extensions to treat as test files.
 config.suffixes = [".ll", ".s", ".test", ".yaml", ".objtxt"]