Tests: Add case for file(LOCK) with lower-cased path

The KWSys update in commit d28e4467 (KWSys 2016-09-14 (c4049689))
fixed this case, so add it to the test suite.

Closes: #16295

Tests/RunCMake/file/LOCK-lowercase.cmake

@@ -0,0 +1,11 @@
+set(lock "${CMAKE_CURRENT_BINARY_DIR}/file-to-lock")
+
+if(WIN32)
+  string(TOLOWER ${lock} lock)
+endif()
+
+file(LOCK ${lock} TIMEOUT 0)
+file(LOCK ${lock} RELEASE)
+
+file(LOCK ${lock} TIMEOUT 0)
+file(LOCK ${lock} RELEASE)

Tests/RunCMake/file/RunCMakeTest.cmake

@@ -22,6 +22,7 @@ run_cmake(LOCK-error-no-result-variable)
 run_cmake(LOCK-error-no-timeout)
 run_cmake(LOCK-error-timeout)
 run_cmake(LOCK-error-unknown-option)
+run_cmake(LOCK-lowercase)
 run_cmake(GLOB)
 run_cmake(GLOB_RECURSE)
 # test is valid both for GLOB and GLOB_RECURSE