bug#52844: missing perl not recognized properly by configure

[Serge Belyshev]

On my systems without perl,  PERL is set to something like

  ${SHELL} '/usr/src/coreutils-9.0/build-aux/missing'  perl

which causes condition at line 70 in configure.ac to fail, resulting in
incorrect detection of perl and subsequent build failure. Suggested fix:

diff --git a/configure.ac b/configure.ac
index 9b8ea0dde..f6a7a6917 100644
--- a/configure.ac
+++ b/configure.ac
@@ -67,7 +67,7 @@ coreutils_MACROS
 # FIXME: this is suboptimal.  Ideally, we would be able to call gl_PERL
 # with an ACTION-IF-NOT-FOUND argument ...
 cu_have_perl=yes
-case $PERL in *"/missing "*) cu_have_perl=no;; esac
+case $PERL in */missing*) cu_have_perl=no;; esac
 AM_CONDITIONAL([HAVE_PERL], [test $cu_have_perl = yes])
 
 # gl_GCC_VERSION_IFELSE([major], [minor], [run-if-found], [run-if-not-found])