Use $(SHELL) and $(KORNSHELL) for shell scripts

Introduce KORNSHELL make variable to point
to the implementation of the Korn Shell.

Use $(SHELL) or $(KORNSHELL) explicitly for
make programs that do not automatically call
shell scripts from the current directory.

cde/config/cf/FreeBSD.cf

@@ -30,6 +30,8 @@ XCOMM operating system:  OSName (OSMajorVersion./**/OSMinorVersion./**/OSTeenyVe
 #endif
 #undef  InstallCmd
 #define InstallCmd		/usr/bin/install
+#undef	KornShell
+#define	KornShell		/usr/local/bin/ksh93
 
 #define UseGas			YES
 #ifndef GccUsesGas