Tests: Cover file(GENERATE) using 'foo.tmp' as input for output 'foo'

Fixes: #20873

Tests/RunCMake/File_Generate/AdjacentInOut.cmake

@@ -0,0 +1,6 @@
+cmake_policy(SET CMP0070 NEW)
+if(EXISTS "${CMAKE_CURRENT_BINARY_DIR}/AdjacentInOut.txt")
+  message(FATAL_ERROR "CMake should not re-run during the build!")
+endif()
+configure_file(AdjacentInOut.in ${CMAKE_CURRENT_BINARY_DIR}/AdjacentInOut.txt.tmp)
+file(GENERATE OUTPUT AdjacentInOut.txt INPUT ${CMAKE_CURRENT_BINARY_DIR}/AdjacentInOut.txt.tmp)

Tests/RunCMake/File_Generate/AdjacentInOut.in

@@ -0,0 +1 @@
+Sample Text File

Tests/RunCMake/File_Generate/RunCMakeTest.cmake

@@ -72,6 +72,7 @@ if (UNIX AND EXISTS /bin/sh)
   if (NOT script_output STREQUAL SUCCESS)
     message(SEND_ERROR "Generated script did not execute correctly:\n${script_output}\n====\n${script_error}")
   endif()
+  unset(RunCMake_TEST_NO_CLEAN)
 endif()
 
 if (RunCMake_GENERATOR MATCHES Makefiles)
@@ -104,3 +105,10 @@ if (RunCMake_GENERATOR MATCHES Makefiles)
     message(SEND_ERROR "File did not re-generate: \"${RunCMake_BINARY_DIR}/ReRunCMake-build/output_file.txt\"")
   endif()
 endif()
+
+set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/AdjacentInOut-build)
+run_cmake(AdjacentInOut)
+set(RunCMake_TEST_NO_CLEAN 1)
+run_cmake_command(AdjacentInOut-nowork ${CMAKE_COMMAND} --build .)
+unset(RunCMake_TEST_BINARY_DIR)
+unset(RunCMake_TEST_NO_CLEAN)