Fix compile when using tcc >0.9.27 on Linux

This allows ksh to be compiled with versions of tcc that define
__dso_handle in libtcc1.a[*], although only on Linux. The two
problems that remain are the following:

1) Older versions of tcc still fail to compile ksh, although now
   they fail after reaching the libdll feature test. I'm not sure
   if fixing that is feasible since even if I hack out the failing
   libdll feature test, ksh fails to link with a '__dso_handle'
   error.
2) tcc fails to build ksh on FreeBSD. For some reason tcc imitates
   GCC on FreeBSD but not on Linux. As a result the FreeBSD math.h
   header tries to define macros that call GCC/Clang builtins.
   This results in undefined symbol errors since tcc doesn't have
   those builtins.

src/cmd/INIT/iffe.sh: compile():
- tcc forbids combining the -c compiler flag with -l* linker flags.
  Strip all -l* flags when -c was passed to the compiler. This is
  only done when tcc is the compiler to prevent build failures on
  some platforms (such as illumos).

src/lib/libast/comp/atexit.c,
src/lib/libast/features/lib,
src/lib/libast/vmalloc/vmexit.c:
- From what I've been able to gather the only OSes with support
  for on_exit are Linux and SunOS 4. However, on_exit takes two
  arguments, so the macro that defines it as taking one argument
  is incorrect. Since Solaris (SunOS 5) no longer has this call
  and the macro breaks on Linux, the clean fix is to remove it
  (atexit(3) is used instead).

[*]: https://repo.or.cz/tinycc.git/commit/dd60b20c6e0d01df8e332b0234125abaa964d324

Progresses: ksh93#232

src/cmd/INIT/iffe.sh

@@ -31,10 +31,24 @@ AIX)	unset LIBPATH ;;
 esac
 
 command=iffe
-version=2021-02-03 # update in USAGE too #
+version=2021-03-21 # update in USAGE too #
 
 compile() # $cc ...
 {
+	# tcc can't combine -l* and -c
+	case "`$1 --version 2> /dev/null`" in
+	tcc*)	if echo "$@" | grep ' -c' | grep -q ' -l'
+		then	for arg
+			do	shift
+				case $arg in
+				-l*) : ;;
+				*) set -- "$@" "$arg"
+				esac
+			done
+		fi
+		;;
+	esac
+
 	"$@" 2>$tmp.err
 	_compile_status=$?
 	if	test -s $tmp.err
@@ -753,7 +767,7 @@ set=
 case `(getopts '[-][123:xyz]' opt --xyz; echo 0$opt) 2>/dev/null` in
 0123)	USAGE=$'
 [-?
-@(#)$Id: iffe (ksh 93u+m) 2021-02-03 $
+@(#)$Id: iffe (ksh 93u+m) 2021-03-21 $
 ]
 [-author?Glenn Fowler <[email protected]>]
 [-author?Phong Vo <[email protected]>]

src/lib/libast/comp/atexit.c

@@ -34,11 +34,7 @@ NoN(atexit)
 
 #else
 
-#if _lib_onexit || _lib_on_exit
-
-#if !_lib_onexit
-#define onexit		on_exit
-#endif
+#if _lib_onexit
 
 extern int		onexit(void(*)(void));
 

src/lib/libast/features/lib

@@ -28,7 +28,7 @@ lib	getopt,getsubopt,getopt_long,getopt_long_only
 lib	glob,index,iswblank,iswctype,killpg,link,localeconv,madvise
 lib	mbtowc,mbrtowc,memalign,memchr,memcpy,memdup,memmove,memset
 lib	mkdir,mkfifo,mktemp,mktime
-lib	mount,on_exit,onexit,opendir,pathconf
+lib	mount,onexit,opendir,pathconf
 lib	readlink,remove,rename,rewinddir,rindex,rmdir,setlocale
 lib	setpgid,setpgrp,setpgrp2,setreuid,setsid,setuid,sigaction
 lib	sigprocmask,sigsetmask,sigunblock,sigvec,socketpair

src/lib/libast/vmalloc/vmexit.c

@@ -93,7 +93,7 @@ int	type;
 	return type;
 }
 
-#endif	/* _lib_onexit || _lib_on_exit */
+#endif	/* _lib_onexit */
 
 #endif /*!PACKAGE_ast*/