build: drop support for building with Watcom

These files are not maintained, they seem to have no users, Watcom
compilers look like not having users nor releases anymore.

Closes curl#5918

Author: bagder

Makefile.dist

@@ -5,7 +5,7 @@
 #                            | (__| |_| |  _ <| |___
 #                             \___|\___/|_| \_\_____|
 #
-# Copyright (C) 1998 - 2018, Daniel Stenberg, <[email protected]>, et al.
+# Copyright (C) 1998 - 2020, Daniel Stenberg, <[email protected]>, et al.
 #
 # This software is licensed as described in the file COPYING, which
 # you should have received as part of this distribution. The terms
@@ -28,18 +28,6 @@ ssl:
 	./configure --with-ssl
 	make
 
-watcom: .SYMBOLIC
-	cd lib && $(MAKE) -u -f Makefile.Watcom
-	cd src && $(MAKE) -u -f Makefile.Watcom
-
-watcom-clean: .SYMBOLIC
-	cd lib && $(MAKE) -u -f Makefile.Watcom clean
-	cd src && $(MAKE) -u -f Makefile.Watcom clean
-
-watcom-vclean: .SYMBOLIC
-	cd lib && $(MAKE) -u -f Makefile.Watcom vclean
-	cd src && $(MAKE) -u -f Makefile.Watcom vclean
-
 mingw32:
 	$(MAKE) -C lib -f Makefile.m32
 	$(MAKE) -C src -f Makefile.m32

lib/Makefile.Watcom

@@ -27,7 +27,7 @@ EXTRA_DIST = Makefile.m32 config-win32.h config-win32ce.h           \
  config-plan9.h config-riscos.h config-mac.h curl_config.h.in       \
  makefile.dj config-dos.h libcurl.plist libcurl.rc config-amigaos.h \
  makefile.amiga Makefile.netware nwlib.c nwos.c config-win32ce.h    \
- config-os400.h setup-os400.h config-symbian.h Makefile.Watcom      \
+ config-os400.h setup-os400.h config-symbian.h                      \
  config-tpf.h mk-ca-bundle.pl mk-ca-bundle.vbs $(CMAKE_DIST)        \
  firefox-db2pem.sh config-vxworks.h Makefile.vxworks checksrc.pl    \
  setup-win32.h