build-sys: use backticks rather than $() for commands in configure

The configure had both backticks and $() in use.  These command
susbstitutions are mutually interchangeable, so one should pick only one
form.  In this case backticks were favored because they are known with
greater range of shells, making the backticks to be more portable.

References: https://www.gnu.org/software/autoconf/manual/autoconf-2.67/html_node/Shell-Substitutions.html#index-g_t_0024_0028_0040var_007bcommands_007d_0029-1632
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

diff --git a/configure.ac b/configure.ac
index 6fae31e93745bb9f8a2547914349ebb98e667a58..7252e9b3530383b350f65e22fbca507d617fc562 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1347,7 +1347,7 @@ AS_IF([test "x$enable_socket_activation" = xyes], [
 
 AC_ARG_WITH([systemdsystemunitdir],
   AS_HELP_STRING([--with-systemdsystemunitdir=DIR], [directory for systemd service files]),
-  [], [with_systemdsystemunitdir=$($PKG_CONFIG --variable=systemdsystemunitdir systemd)])
+  [], [with_systemdsystemunitdir=`$PKG_CONFIG --variable=systemdsystemunitdir systemd`])
 
 AS_IF([test "x$with_systemdsystemunitdir" != "xno"], [
   AC_SUBST([systemdsystemunitdir], [$with_systemdsystemunitdir])
@@ -1359,8 +1359,8 @@ AM_CONDITIONAL([HAVE_SYSTEMD], [test -n "$with_systemdsystemunitdir" -a "x$with_
 AC_ARG_WITH([bashcompletiondir],
   AS_HELP_STRING([--with-bashcompletiondir=DIR], [Bash completions directory]),
   [],
-  [AS_IF([$($PKG_CONFIG --exists bash-completion)], [
-    with_bashcompletiondir=$($PKG_CONFIG --variable=completionsdir bash-completion)
+  [AS_IF([`$PKG_CONFIG --exists bash-completion`], [
+    with_bashcompletiondir=`$PKG_CONFIG --variable=completionsdir bash-completion`
   ], [
     with_bashcompletiondir=${datadir}/bash-completion/completions
   ])