Test CMP0015 OLD and NEW link_directories behavior

We create a LinkDirectory test to check that the policy OLD and NEW
behaviors work as documented.  See issue #9697.

Tests/CMakeLists.txt

@@ -122,6 +122,7 @@ IF(BUILD_TESTING)
   ADD_TEST_MACRO(SetLang SetLang)
   ADD_TEST_MACRO(ExternalOBJ ExternalOBJ)
   ADD_TEST_MACRO(LoadCommand LoadedCommand)
+  ADD_TEST_MACRO(LinkDirectory bin/LinkDirectory)
   ADD_TEST_MACRO(LinkLanguage LinkLanguage)
   ADD_TEST_MACRO(LinkLine LinkLine)
   ADD_TEST_MACRO(MacroTest miniMacroTest)

Tests/LinkDirectory/CMakeLists.txt

@@ -0,0 +1,47 @@
+cmake_minimum_required(VERSION 2.8)
+project(LinkDirectory C)
+
+# Put the subproject source tree in our build tree so it can refer to
+# link directories relative to its source.
+if(NOT "${LinkDirectory_SOURCE_DIR}" STREQUAL "${LinkDirectory_BINARY_DIR}")
+  file(COPY External/ DESTINATION External PATTERN CVS EXCLUDE)
+endif()
+
+# Build a library into the subproject source tree.
+add_library(mylibA STATIC mylibA.c)
+set_property(TARGET mylibA PROPERTY
+  ARCHIVE_OUTPUT_DIRECTORY "${LinkDirectory_BINARY_DIR}/External/lib")
+get_property(mylibA TARGET mylibA PROPERTY LOCATION)
+
+# Build a library into our build tree relative to the subproject build tree.
+add_library(mylibB STATIC mylibB.c)
+set_property(TARGET mylibB PROPERTY
+  ARCHIVE_OUTPUT_DIRECTORY "${LinkDirectory_BINARY_DIR}/lib")
+get_property(mylibB TARGET mylibB PROPERTY LOCATION)
+
+# Create a custom target to drive the subproject build.
+include(ExternalProject)
+ExternalProject_Add(ExternalTarget
+  SOURCE_DIR "${LinkDirectory_BINARY_DIR}/External"
+  BINARY_DIR "${LinkDirectory_BINARY_DIR}/External-build"
+  CMAKE_ARGS "-DCMAKE_RUNTIME_OUTPUT_DIRECTORY=${LinkDirectory_BINARY_DIR}/bin"
+  PREFIX "${LinkDirectory_BINARY_DIR}/External-build/root"
+  DOWNLOAD_COMMAND ""
+  INSTALL_COMMAND ""
+  )
+
+# Add a step to wipe out the subproject executable after our libraries
+# change.  This is needed because the subproject cannot depend on them
+# directly because it does not know the full paths to the libraries.
+# (The purpose of this test is to check that link_directories works.)
+ExternalProject_Add_Step(ExternalTarget cleanup
+  COMMAND ${CMAKE_COMMAND} -E remove_directory ${LinkDirectory_BINARY_DIR}/bin
+  DEPENDEES download
+  DEPENDERS configure
+  DEPENDS ${mylibA} ${mylibB}
+    "${LinkDirectory_BINARY_DIR}/External/CMakeLists.txt"
+    "${LinkDirectory_BINARY_DIR}/External/myexe.c"
+  )
+
+# Make the subproject build after our targets.
+add_dependencies(ExternalTarget mylibA mylibB)

Tests/LinkDirectory/External/CMakeLists.txt

@@ -0,0 +1,14 @@
+cmake_minimum_required(VERSION 2.8)
+project(LinkDirectoryExternal C)
+
+# Test CMP0015 OLD behavior: -L../lib
+cmake_policy(SET CMP0015 OLD)
+link_directories(../lib)
+
+# Test CMP0015 NEW behavior: -L${CMAKE_CURRENT_SOURCE_DIR}/lib
+cmake_policy(SET CMP0015 NEW)
+link_directories(lib)
+
+add_executable(myexe myexe.c)
+set_property(TARGET myexe PROPERTY OUTPUT_NAME LinkDirectory)
+target_link_libraries(myexe mylibA mylibB)

Tests/LinkDirectory/External/myexe.c

@@ -0,0 +1,3 @@
+extern int mylibA(void);
+extern int mylibB(void);
+int main(void) { return mylibA() + mylibB(); }

Tests/LinkDirectory/mylibA.c

@@ -0,0 +1 @@
+int mylibA(void) { return 0; }

Tests/LinkDirectory/mylibB.c

@@ -0,0 +1 @@
+int mylibB(void) { return 0; }