build-sys: remove unused LIBS

Since meson switch and commit feabc71 ("configure: do not include
dependency flags in QEMU_CFLAGS and LIBS"), LIBS is unused.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210114125605.1227742-2-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -3385,16 +3385,6 @@ else
   for pthread_lib in $PTHREADLIBS_LIST; do
     if compile_prog "" "$pthread_lib" ; then
       pthread=yes
-      found=no
-      for lib_entry in $LIBS; do
-        if test "$lib_entry" = "$pthread_lib"; then
-          found=yes
-          break
-        fi
-      done
-      if test "$found" = "no"; then
-        LIBS="$pthread_lib $LIBS"
-      fi
       break
     fi
   done
@@ -4083,28 +4073,6 @@ if compile_prog "" "" ; then
   bswap_h=yes
 fi
 
-##########################################
-# Do we need librt
-# uClibc provides 2 versions of clock_gettime(), one with realtime
-# support and one without. This means that the clock_gettime() don't
-# need -lrt. We still need it for timer_create() so we check for this
-# function in addition.
-cat > $TMPC <<EOF
-#include <signal.h>
-#include <time.h>
-int main(void) {
-  timer_create(CLOCK_REALTIME, NULL, NULL);
-  return clock_gettime(CLOCK_REALTIME, NULL);
-}
-EOF
-
-if compile_prog "" "" ; then
-  :
-# we need pthread for static linking. use previous pthread test result
-elif compile_prog "" "$pthread_lib -lrt" ; then
-  LIBS="$LIBS -lrt"
-fi
-
 # Check whether we have openpty() in either libc or libutil
 cat > $TMPC << EOF
 extern int openpty(int *am, int *as, char *name, void *termp, void *winp);