Try to make the macros do almost nothing for Watcom.

Modules/GenerateExportHeader.cmake

@@ -160,7 +160,13 @@ macro(_test_compiler_hidden_visibility)
   # Exclude XL here because it misinterprets -fvisibility=hidden even though
   # the check_cxx_compiler_flag passes
   # http://www.cdash.org/CDash/testDetails.php?test=109109951&build=1419259
-  if (NOT GCC_TOO_OLD AND NOT _INTEL_TOO_OLD AND NOT WIN32 AND NOT CYGWIN AND NOT "${CMAKE_CXX_COMPILER_ID}" MATCHES XL AND NOT "${CMAKE_CXX_COMPILER_ID}" MATCHES PGI)
+  if (NOT GCC_TOO_OLD
+      AND NOT _INTEL_TOO_OLD
+      AND NOT WIN32
+      AND NOT CYGWIN
+      AND NOT "${CMAKE_CXX_COMPILER_ID}" MATCHES XL
+      AND NOT "${CMAKE_CXX_COMPILER_ID}" MATCHES PGI
+      AND NOT "${CMAKE_CXX_COMPILER_ID}" MATCHES Watcom)
     check_cxx_compiler_flag(-fvisibility=hidden COMPILER_HAS_HIDDEN_VISIBILITY)
     check_cxx_compiler_flag(-fvisibility-inlines-hidden COMPILER_HAS_HIDDEN_INLINE_VISIBILITY)
     option(USE_COMPILER_HIDDEN_VISIBILITY "Use HIDDEN visibility support if available." ON)
@@ -169,7 +175,11 @@ macro(_test_compiler_hidden_visibility)
 endmacro()
 
 macro(_test_compiler_has_deprecated)
-  if("${CMAKE_CXX_COMPILER_ID}" MATCHES Borland OR "${CMAKE_CXX_COMPILER_ID}" MATCHES HP OR GCC_TOO_OLD OR "${CMAKE_CXX_COMPILER_ID}" MATCHES PGI)
+  if("${CMAKE_CXX_COMPILER_ID}" MATCHES Borland
+      OR "${CMAKE_CXX_COMPILER_ID}" MATCHES HP
+      OR GCC_TOO_OLD
+      OR "${CMAKE_CXX_COMPILER_ID}" MATCHES PGI
+      OR "${CMAKE_CXX_COMPILER_ID}" MATCHES Watcom)
     set(COMPILER_HAS_DEPRECATED "" CACHE INTERNAL "Compiler support for a deprecated attribute")
   else()
     _check_cxx_compiler_attribute("__attribute__((__deprecated__))" COMPILER_HAS_DEPRECATED_ATTR)