Revert "[gn build] Manually port 90ccf21"

This reverts commit 46307f1.
90ccf21 was reverted in 030ee84.

Author: nico

llvm/utils/gn/secondary/clang/test/BUILD.gn

@@ -65,8 +65,6 @@ write_lit_config("lit_site_cfg") {
     "CMAKE_C_COMPILER=cc",
     "ENABLE_BACKTRACES=1",
     "ENABLE_SHARED=0",
-    "LLVM_BUILD_EXAMPLES=0",
-    "LLVM_BYE_LINK_INTO_TOOLS=0",
     "LLVM_EXTERNAL_LIT=",
     "LLVM_HOST_TRIPLE=$llvm_current_triple",
     "LLVM_LIT_TOOLS_DIR=",  # Intentionally empty, matches cmake build.
@@ -113,37 +111,26 @@ write_lit_config("lit_site_cfg") {
   }
 
   if (host_os == "mac") {
-    extra_values += [
-      "LLVM_PLUGIN_EXT=.dylib",
-      "SHLIBEXT=.dylib",
-    ]
+    extra_values += [ "LLVM_PLUGIN_EXT=.dylib" ]
   } else if (host_os == "win") {
-    extra_values += [
-      "LLVM_PLUGIN_EXT=.dll",
-      "SHLIBEXT=.dll",
-    ]
+    extra_values += [ "LLVM_PLUGIN_EXT=.dll" ]
   } else {
-    extra_values += [
-      "LLVM_PLUGIN_EXT=.so",
-      "SHLIBEXT=.so",
-    ]
+    extra_values += [ "LLVM_PLUGIN_EXT=.so" ]
   }
 
   if (host_os == "win") {
     extra_values += [
       # See comment for Windows solink in llvm/utils/gn/build/toolchain/BUILD.gn
       "CMAKE_LIBRARY_OUTPUT_DIRECTORY=" + rebase_path("$root_out_dir/bin", dir),
-      "LLVM_ENABLE_PLUGINS=1",
       "LLVM_LIT_ERRC_MESSAGES=no such file or directory;is a directory;" +
           "invalid argument;permission denied",
-      "PERL_EXECUTABLE=",
+      "PERL_EXECUTABLE="
     ]
   } else {
     extra_values += [
       "CMAKE_LIBRARY_OUTPUT_DIRECTORY=" + rebase_path("$root_out_dir/lib", dir),
-      "LLVM_ENABLE_PLUGINS=1",
       "LLVM_LIT_ERRC_MESSAGES=",
-      "PERL_EXECUTABLE=/usr/bin/perl",
+      "PERL_EXECUTABLE=/usr/bin/perl"
     ]
   }