configure.ac: check pdflatex is available to build documentation

configure.ac

@@ -2175,11 +2175,15 @@ AC_ARG_ENABLE(build-doc, [AS_HELP_STRING([--disable-build-doc],
 			[disable building of documentation])],
 			enable_build_doc=$enableval, enable_build_doc=yes)
 
-# Check whether doxygen is installed
+# Check whether doxygen and pdflatex are installed
 AC_PATH_PROG(doxygencommand, doxygen)
 if test "$doxygencommand" = "" ; then
 	enable_build_doc="no"
 fi
+AC_PATH_PROG(pdflatex, pdflatex)
+if test "pdflatexcommand" = "" ; then
+	enable_build_doc="no"
+fi
 
 AM_CONDITIONAL(BUILD_DOC, [test x$enable_build_doc != xno])