Tests: Generalize RunCMake.SymlinkTrees implementation

Accept paths to the source and binary directories as arguments.
Prepare to support more ways of passing the source and binary
directories to `cmake`.

Tests/RunCMake/SymlinkTrees/RunCMakeTest.cmake

@@ -1,19 +1,37 @@
 include(RunCMake)
 
+function(run_symlink_test_case)
+  file(REMOVE_RECURSE
+    "${RunCMake_TEST_BINARY_DIR}/CMakeCache.txt"
+    "${RunCMake_TEST_BINARY_DIR}/CMakeFiles"
+    )
+  run_cmake_with_options(${ARGN})
+endfunction()
+
 # This function assumes that ``${RunCMake_BINARY_DIR}/${name}/source`` and
 # ``${RunCMake_BINARY_DIR}/${name}/binary`` are set up properly prior to
 # calling it.
-function (run_symlink_test name)
+function (run_symlink_test case src bin)
+  string(REGEX REPLACE "-.*" "" name "${case}")
   set(RunCMake_TEST_NO_CLEAN TRUE)
+  set(RunCMake_TEST_SOURCE_DIR "${RunCMake_BINARY_DIR}/${name}/${src}")
+  set(RunCMake_TEST_BINARY_DIR "${RunCMake_BINARY_DIR}/${name}/${bin}")
   configure_file(
     "${CMAKE_CURRENT_LIST_DIR}/CMakeLists.txt"
-    "${RunCMake_BINARY_DIR}/${name}/source/CMakeLists.txt"
+    "${RunCMake_TEST_SOURCE_DIR}/CMakeLists.txt"
     COPYONLY)
-  set(RunCMake_TEST_SOURCE_DIR "${RunCMake_BINARY_DIR}/${name}/source")
-  set(RunCMake_TEST_BINARY_DIR "${RunCMake_BINARY_DIR}/${name}/binary")
+
+  # We explicitly pass the source directory argument for each case.
+  set(RunCMake_TEST_NO_SOURCE_DIR 1)
+
+  # Test running in binary directory.
+  set(RunCMake_TEST_COMMAND_WORKING_DIRECTORY "${RunCMake_TEST_BINARY_DIR}")
   # Emulate a shell using this directory.
-  set(ENV{PWD} "${RunCMake_TEST_BINARY_DIR}")
-  run_cmake("${name}_symlinks")
+  set(ENV{PWD} "${RunCMake_TEST_COMMAND_WORKING_DIRECTORY}")
+
+  # Pass absolute path to the source tree, plain.
+  set(RunCMake_TEST_VARIANT_DESCRIPTION " $abs/${name}/${src}")
+  run_symlink_test_case("${case}" "${RunCMake_TEST_SOURCE_DIR}")
 endfunction ()
 
 # Create the following structure:
@@ -21,12 +39,9 @@ endfunction ()
 #   .../common_real/source
 #   .../common_real/binary
 #   .../common -> common_real
-#
-# In this case, CMake should act as if .../common *is* .../common_real for all
-# computations except ``REALPATH``.  This supports the case where a system has
-# a stable *symlink*, but not a stable target for that symlink.
 file(REMOVE_RECURSE "${RunCMake_BINARY_DIR}/common_real")
 file(REMOVE "${RunCMake_BINARY_DIR}/common")
 file(MAKE_DIRECTORY "${RunCMake_BINARY_DIR}/common_real/source")
+file(MAKE_DIRECTORY "${RunCMake_BINARY_DIR}/common_real/binary")
 file(CREATE_LINK "common_real" "${RunCMake_BINARY_DIR}/common" SYMBOLIC)
-run_symlink_test(common)
+run_symlink_test(common-separate "source" "binary")