OpenWatcom: fix Linux support file

Fix CMAKE_SHARED_LINKER_FLAGS_INIT macro
Fix executable file name for Linux to be without extension
Add system header files directory for cross-compilation
5 jobs for !4699 with patch-12 in 3 minutes and 57 seconds (queued for 1 second)
detached
Status Name Job ID Coverage
  Build
passed build:debian10-iwyu #4930906
build docker linux

00:01:24

passed build:fedora31-tidy #4930907
build docker linux

00:03:57

 
  External
passed cdash

passed ghostflow-check-master

passed cdash