Tests: Add tests for install(<TARGETS|FILES> ... OPTIONAL)

Tests/RunCMake/install/FILES-OPTIONAL-all-check.cmake

@@ -0,0 +1 @@
+check_installed([[^src;src/main.c$]])

Tests/RunCMake/install/FILES-OPTIONAL.cmake

@@ -0,0 +1 @@
+install(FILES main.c noexist.c DESTINATION src OPTIONAL)

Tests/RunCMake/install/RunCMakeTest.cmake

@@ -73,6 +73,8 @@ if(NOT RunCMake_GENERATOR STREQUAL "Xcode" OR NOT "$ENV{CMAKE_OSX_ARCHITECTURES}
 endif()
 
 run_install_test(TARGETS-InstallFromSubDir)
+run_install_test(TARGETS-OPTIONAL)
+run_install_test(FILES-OPTIONAL)
 
 set(run_install_test_components 1)
 run_install_test(FILES-EXCLUDE_FROM_ALL)

Tests/RunCMake/install/TARGETS-OPTIONAL-all-check.cmake

@@ -0,0 +1 @@
+check_installed([[^bin;bin/myexe(\.exe)?$]])

Tests/RunCMake/install/TARGETS-OPTIONAL-stderr.txt

@@ -0,0 +1 @@
+^WARNING: Target "notall" has EXCLUDE_FROM_ALL set and will not be built by default but an install rule has been provided for it\.  CMake does not define behavior for this case\.$

Tests/RunCMake/install/TARGETS-OPTIONAL.cmake

@@ -0,0 +1,4 @@
+enable_language(C)
+add_executable(myexe main.c)
+add_executable(notall EXCLUDE_FROM_ALL main.c)
+install(TARGETS myexe notall DESTINATION bin OPTIONAL)