[HIPIFY][cmake] Fix require_program function

Function require_program erroneously doesn't report "Can't find program" on any missing program except the first one due to the cached FOUND_PROGRAM value.

Additionally:
+ Do not throw FATAL_ERROR on missing program in order to obtain the whole list of missing programs (if any).
+ Report also found program location.

hipamd/hipify-clang/CMakeLists.txt

@@ -68,9 +68,11 @@ if (HIPIFY_CLANG_TESTS)
     find_package(PythonInterp 2.7 REQUIRED EXACT)
 
     function (require_program PROGRAM_NAME)
-        find_program(FOUND_PROGRAM ${PROGRAM_NAME})
-        if (NOT FOUND_PROGRAM)
-            message(FATAL_ERROR "Can't find ${PROGRAM_NAME}. Either set HIPIFY_CLANG_TESTS to OFF to disable hipify tests, or install the missing program.")
+        find_program(FOUND_${PROGRAM_NAME} ${PROGRAM_NAME})
+        if (FOUND_${PROGRAM_NAME})
+            message(STATUS "Found ${PROGRAM_NAME}: ${FOUND_${PROGRAM_NAME}}")
+        else()
+            message(SEND_ERROR "Can't find ${PROGRAM_NAME}. Either set HIPIFY_CLANG_TESTS to OFF to disable hipify tests, or install the missing program.")
         endif()
     endfunction()