Remove hard-coded version of RTDLL for Open Watcom

In InstallRequiredSystemLibraries the version number for RTDLL can be
calculated from the compiler version.  This will support current and
future OW versions without updating the module again.

Modules/InstallRequiredSystemLibraries.cmake

@@ -366,18 +366,22 @@ endif()
 
 if(WATCOM)
   get_filename_component( CompilerPath ${CMAKE_C_COMPILER} PATH )
-  if(WATCOM17)
-     set( __install__libs ${CompilerPath}/clbr17.dll
-       ${CompilerPath}/mt7r17.dll ${CompilerPath}/plbr17.dll )
-  endif()
-  if(WATCOM18)
-     set( __install__libs ${CompilerPath}/clbr18.dll
-       ${CompilerPath}/mt7r18.dll ${CompilerPath}/plbr18.dll )
+  if(CMAKE_C_COMPILER_VERSION)
+    set(_compiler_version ${CMAKE_C_COMPILER_VERSION})
+  else()
+    set(_compiler_version ${CMAKE_CXX_COMPILER_VERSION})
   endif()
-  if(WATCOM19)
-     set( __install__libs ${CompilerPath}/clbr19.dll
-       ${CompilerPath}/mt7r19.dll ${CompilerPath}/plbr19.dll )
+  string(REGEX MATCHALL "[0-9]+" _watcom_version_list "${_compiler_version}")
+  list(GET _watcom_version_list 0 _watcom_major)
+  list(GET _watcom_version_list 1 _watcom_minor)
+  if(${_watcom_major} GREATER 11)
+    math(EXPR _watcom_major "${_watcom_major} - 11")
   endif()
+  math(EXPR _watcom_minor "${_watcom_minor} / 10")
+  set( __install__libs
+    ${CompilerPath}/clbr${_watcom_major}${_watcom_minor}.dll
+    ${CompilerPath}/mt7r${_watcom_major}${_watcom_minor}.dll
+    ${CompilerPath}/plbr${_watcom_major}${_watcom_minor}.dll )
   foreach(lib
       ${__install__libs}
       )