Disable parallel make jobs so that `st_crypt.h` can find `<cryptlib.h>`.
As of writing, I have no idea how to fix this otherwise.

From: Seth M. Price <sprice623@aol.com>

--- a/src/syncterm/GNUmakefile
+++ b/src/syncterm/GNUmakefile
@@ -96,6 +96,8 @@ ifndef bcc
  endif
 endif
 
+.NOTPARALLEL:
+
 $(MTOBJODIR)$(DIRSEP)ciolib_res$(OFILE):
 	cd ${MTOBJODIR} && $(AR) -x ../${CIOLIB-MT} ciolib_res$(OFILE)