Revert "[CMake][LIT] Add option to run lit testsuites in parallel" (#84813)

Reverts #82899

Per the discussion on the PR, this needs more design and justification.

Author: Jeff Niu

llvm/CMakeLists.txt

@@ -712,8 +712,6 @@ if(LLVM_INDIVIDUAL_TEST_COVERAGE)
 endif()
 set(LLVM_LIT_ARGS "${LIT_ARGS_DEFAULT}" CACHE STRING "Default options for lit")
 
-option(LLVM_PARALLEL_LIT "Enable multiple lit suites to run in parallel" OFF)
-
 # On Win32 hosts, provide an option to specify the path to the GnuWin32 tools.
 if( WIN32 AND NOT CYGWIN )
   set(LLVM_LIT_TOOLS_DIR "" CACHE PATH "Path to GnuWin32 tools")

llvm/cmake/modules/AddLLVM.cmake

@@ -1947,18 +1947,11 @@ function(add_lit_target target comment)
     list(APPEND LIT_COMMAND --param ${param})
   endforeach()
   if (ARG_UNPARSED_ARGUMENTS)
-    if (LLVM_PARALLEL_LIT)
-     add_custom_target(${target}
-       COMMAND ${LIT_COMMAND} ${ARG_UNPARSED_ARGUMENTS}
-       COMMENT "${comment}"
-       )
-    else()
-     add_custom_target(${target}
-       COMMAND ${LIT_COMMAND} ${ARG_UNPARSED_ARGUMENTS}
-       COMMENT "${comment}"
-       USES_TERMINAL
-       )
-    endif()
+    add_custom_target(${target}
+      COMMAND ${LIT_COMMAND} ${ARG_UNPARSED_ARGUMENTS}
+      COMMENT "${comment}"
+      USES_TERMINAL
+      )
   else()
     add_custom_target(${target}
       COMMAND ${CMAKE_COMMAND} -E echo "${target} does nothing, no tools built.")

llvm/docs/CMake.rst

@@ -762,12 +762,6 @@ enabled sub-projects. Nearly all of these variable names begin with
 **LLVM_PARALLEL_LINK_JOBS**:STRING
   Define the maximum number of concurrent link jobs.
 
-**LLVM_PARALLEL_LIT**:BOOL
-  Defaults to ``OFF``. If set to ``OFF``, lit testsuites will be configured
-  with CMake's ``USES_TERMINAL`` flag to give direct access to the terminal. If
-  set to ``ON``, that flag will be removed allowing Ninja to schedule multiple
-  lit testsuites in parallel.
-
 **LLVM_RAM_PER_COMPILE_JOB**:STRING
   Calculates the amount of Ninja compile jobs according to available resources.
   Value has to be in MB, overwrites LLVM_PARALLEL_COMPILE_JOBS. Compile jobs