Fix AC_ARG_WITH syntax

configure.ac

@@ -26,14 +26,14 @@ AC_ARG_WITH([rst2man],
 		[--with-rst2man=PATH],
 		[Location of rst2man (auto)]),
 	[RST2MAN="$withval"],
-	AC_CHECK_PROGS(RST2MAN, [rst2man rst2man.py], []))
+	[AC_CHECK_PROGS(RST2MAN, [rst2man rst2man.py], [])])
 
 AC_ARG_WITH([lcov],
 	AS_HELP_STRING(
 		[--with-lcov=PATH],
 		[Location of lcov to generate coverage data (auto)]),
 	[LCOV="$withval"],
-	AC_CHECK_PROGS(LCOV, [lcov], []))
+	[AC_CHECK_PROGS(LCOV, [lcov], [])])
 AM_CONDITIONAL(HAVE_LCOV, [test -n "$LCOV"])
 
 AC_ARG_WITH([genhtml],
@@ -41,7 +41,7 @@ AC_ARG_WITH([genhtml],
 		[--with-genhtml=PATH],
 		[Location of genhtml to generate coverage reports (auto)]),
 	[GENHTML="$withval"],
-	AC_CHECK_PROGS(GENHTML, [genhtml], []))
+	[AC_CHECK_PROGS(GENHTML, [genhtml], [])])
 AM_CONDITIONAL(HAVE_GENHTML, [test -n "$GENHTML"])
 
 AC_ARG_WITH([pandoc],
@@ -49,7 +49,7 @@ AC_ARG_WITH([pandoc],
 		[--with-pandoc=PATH],
 		[Location of pandoc to generate README.md (auto)]),
 	[PANDOC="$withval"],
-	AC_CHECK_PROGS(PANDOC, [pandoc], []))
+	[AC_CHECK_PROGS(PANDOC, [pandoc], [])])
 AM_CONDITIONAL(HAVE_PANDOC, [test -n "$PANDOC"])
 
 m4_ifndef([VARNISH_PREREQ], AC_MSG_ERROR([Need varnish.m4 -- see INSTALL.rst]))