Fix CHECK_(C|CXX)_COMPILER_FLAG for HP

This compiler warns and returns 0 for unrecognized flags.  We fix the
compiler flag check macros by looking for a warning in the output.
See issue #9516.

Modules/CheckCCompilerFlag.cmake

@@ -21,6 +21,7 @@ MACRO (CHECK_C_COMPILER_FLAG _FLAG _RESULT)
      # Some compilers do not fail with a bad flag
      FAIL_REGEX "unrecognized option"                       # GNU
      FAIL_REGEX "ignoring unknown option"                   # MSVC
+     FAIL_REGEX "[Uu]nknown option"                         # HP
      )
    SET (CMAKE_REQUIRED_DEFINITIONS "${SAFE_CMAKE_REQUIRED_DEFINITIONS}")
 ENDMACRO (CHECK_C_COMPILER_FLAG)

Modules/CheckCXXCompilerFlag.cmake

@@ -21,6 +21,7 @@ MACRO (CHECK_CXX_COMPILER_FLAG _FLAG _RESULT)
      # Some compilers do not fail with a bad flag
      FAIL_REGEX "unrecognized option"                       # GNU
      FAIL_REGEX "ignoring unknown option"                   # MSVC
+     FAIL_REGEX "[Uu]nknown option"                         # HP
      )
    SET (CMAKE_REQUIRED_DEFINITIONS "${SAFE_CMAKE_REQUIRED_DEFINITIONS}")
 ENDMACRO (CHECK_CXX_COMPILER_FLAG)