Improve error message for bad arguments to script

	* generate_libstdcxx_web_docs: Improve error output.

From-SVN: r269169

maintainer-scripts/ChangeLog

+2019-02-23  Jonathan Wakely  <jwakely@redhat.com>
+
+	* generate_libstdcxx_web_docs: Improve error output.
+
 2018-11-22  Martin Liska  <mliska@suse.cz>
 
 	* bugzilla-close-candidate.py: New file.

maintainer-scripts/generate_libstdcxx_web_docs

@@ -3,16 +3,28 @@
 # i.e. http://gcc.gnu.org/onlinedocs/gcc-x.y.z/libstdc++*
 
 SRCDIR=${1}
-DOCSDIR=$(realpath ${2})
+DOCSDIR=${2}
 
 if ! [ $# -eq 2 -a -x "${SRCDIR}/configure" -a -d "${DOCSDIR}" ]
 then
+  if ! [ $# -eq 2 ]
+  then
+    echo "$0: Wrong number of arguments" >&2
+  elif ! [ -x "${SRCDIR}/configure" ]
+  then
+    echo "$0: No executable configure script found in $SRCDIR" >&2
+  elif ! [ -d "${DOCSDIR}" ]
+  then
+    echo "$0: Output directory does not exist: $DOCSDIR" >&2
+  fi
   echo "Usage: $0 <gcc src dir> <doc output dir>" >&2
   exit 1
 fi
 
 set -e
 
+DOCSDIR=$(realpath ${DOCSDIR})
+
 # Check we have some of the required tools
 for i in doxygen dot dblatex pdflatex makeindex
 do