installworld: improve portability of ldd use

b3b462229f added a case statement to ignore lines containing strings
in square brackets such as "[vdso]" and "[preloaded]". On MacOS
Monterey where /bin/sh may be zsh, this fails with:

/bin/sh: -c: line 0: syntax error near unexpected token `;;'

Invoke grep in the pipeline to remove such lines instead.

Reviewed by:	emaste
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D35618

Makefile.inc1

@@ -1368,12 +1368,8 @@ distributeworld installworld stageworld: _installcheck_world .PHONY
 		fi; \
 	    done); \
 	if [ -z "${CROSSBUILD_HOST}" ] ; then \
-		libs=$$(ldd -f "%o %p\n" -f "%o %p\n" $$progs 2>/dev/null | sort -u | \
+		libs=$$(ldd -f "%o %p\n" -f "%o %p\n" $$progs 2>/dev/null | sort -u | grep -Ev '\[.*]' | \
 		    while read line; do \
-			case $$line in \
-			"["*"]") \
-				continue;; \
-			esac; \
 			set -- $$line; \
 			if [ "$$2 $$3" != "not found" ]; then \
 				echo $$2; \