patch 8.2.2852: configure can add --as-needed a second time

Problem:    Configure can add --as-needed a second time.
Solution:   Only add --as-needed if not already there.  (Natanael Copa,
            closes #8189, closes #8181)
diff --git a/src/configure.ac b/src/configure.ac
index 657cc97..cc8d61f 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -4519,7 +4519,9 @@
 LINK_AS_NEEDED=
 # Check if linker supports --as-needed and --no-as-needed options
 if $CC -Wl,--help 2>/dev/null | grep as-needed > /dev/null; then
-  LDFLAGS=`echo "$LDFLAGS" | sed -e 's/ *-Wl,--as-needed//g' | sed -e 's/$/ -Wl,--as-needed/'`
+  if ! echo "$LDFLAGS" | grep -q -- '-Wl,[[^[:space:]]]*--as-needed'; then
+    LDFLAGS="$LDFLAGS -Wl,--as-needed"
+  fi
   LINK_AS_NEEDED=yes
 fi
 if test "$LINK_AS_NEEDED" = yes; then