build: Drop unused use_pkgconfig variable

configure.ac

@@ -573,7 +573,6 @@ AC_ARG_WITH([daemon],
   [build_bitcoind=$withval],
   [build_bitcoind=yes])
 
-use_pkgconfig=yes
 case $host in
   *mingw*)
      TARGET_OS=windows
@@ -678,14 +677,10 @@ case $host in
      ;;
 esac
 
-if test x$use_pkgconfig = xyes; then
-  m4_ifndef([PKG_PROG_PKG_CONFIG], [AC_MSG_ERROR(PKG_PROG_PKG_CONFIG macro not found. Please install pkg-config and re-run autogen.sh.)])
-  m4_ifdef([PKG_PROG_PKG_CONFIG], [
-  PKG_PROG_PKG_CONFIG
-  if test x"$PKG_CONFIG" = "x"; then
-    AC_MSG_ERROR(pkg-config not found.)
-  fi
-  ])
+m4_ifndef([PKG_PROG_PKG_CONFIG], [AC_MSG_ERROR([PKG_PROG_PKG_CONFIG macro not found. Please install pkg-config and re-run autogen.sh])])
+PKG_PROG_PKG_CONFIG
+if test "x$PKG_CONFIG" = x; then
+  AC_MSG_ERROR([pkg-config not found])
 fi
 
 if test x$use_extended_functional_tests != xno; then