[CMake] Do not set CMP0116 explicitly to old

CMP0116 was originally set to old to get rid of warnings. However, this
behavior is now set to new by default with the minimum CMake version that LLVM
requires so does not produce any warnings, and setting it explicitly to old
does produce a warning in newer CMake versions. Due to these reasons, remove
this check for now.

Splitting off from removing the CMP0114 check just in case something breaks.

This also removes two instances of a workaround related to the old
behavior of CMP0116.

Partially fixes #83727.

Author: boomanaiden154

cmake/Modules/CMakePolicy.cmake

@@ -1,11 +1,5 @@
 # CMake policy settings shared between LLVM projects
 
-# CMP0116: Ninja generators transform `DEPFILE`s from `add_custom_command()`
-# New in CMake 3.20. https://cmake.org/cmake/help/latest/policy/CMP0116.html
-if(POLICY CMP0116)
-  cmake_policy(SET CMP0116 OLD)
-endif()
-
 # MSVC debug information format flags are selected via
 # CMAKE_MSVC_DEBUG_INFORMATION_FORMAT, instead of
 # embedding flags in e.g. CMAKE_CXX_FLAGS_RELEASE.

llvm/cmake/modules/TableGen.cmake

@@ -23,18 +23,13 @@ function(tablegen project ofn)
 
   # Use depfile instead of globbing arbitrary *.td(s) for Ninja.
   if(CMAKE_GENERATOR MATCHES "Ninja")
-    # Make output path relative to build.ninja, assuming located on
-    # ${CMAKE_BINARY_DIR}.
     # CMake emits build targets as relative paths but Ninja doesn't identify
-    # absolute path (in *.d) as relative path (in build.ninja)
-    # Note that tblgen is executed on ${CMAKE_BINARY_DIR} as working directory.
-    file(RELATIVE_PATH ofn_rel
-      ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR}/${ofn})
+    # absolute path (in *.d) as relative path (in build.ninja). Post CMP0116,
+    # CMake handles this discrepancy for us.
     set(additional_cmdline
-      -o ${ofn_rel}
-      -d ${ofn_rel}.d
-      WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
-      DEPFILE ${CMAKE_CURRENT_BINARY_DIR}/${ofn}.d
+      -o ${ofn}
+      -d ${ofn}.d
+      DEPFILE ${ofn}.d
       )
     set(local_tds)
     set(global_tds)

mlir/cmake/modules/AddMLIR.cmake

@@ -47,15 +47,12 @@ function(_pdll_tablegen project ofn)
     # Make output path relative to build.ninja, assuming located on
     # ${CMAKE_BINARY_DIR}.
     # CMake emits build targets as relative paths but Ninja doesn't identify
-    # absolute path (in *.d) as relative path (in build.ninja)
-    # Note that tblgen is executed on ${CMAKE_BINARY_DIR} as working directory.
-    file(RELATIVE_PATH ofn_rel
-      ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR}/${ofn})
+    # absolute path (in *.d) as relative path (in build.ninja). Post CMP0116,
+    # CMake handles this discrepancy for us.
     set(additional_cmdline
-      -o ${ofn_rel}
-      -d ${ofn_rel}.d
-      WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
-      DEPFILE ${CMAKE_CURRENT_BINARY_DIR}/${ofn}.d
+      -o ${ofn}
+      -d ${ofn}.d
+      DEPFILE ${ofn}.d
       )
     set(local_tds)
     set(global_tds)