build: Fix libgcrypt detection on FHS systems.

Reported by Christopher Allan Webber <cwebber@dustycloud.org>.

* m4/guix.m4 (GUIX_LIBGCRYPT_LIBDIR): Add "grep -e -L" to the pipeline
  to account for cases where the output of "libgcrypt-config --libs"
  lacks a -L flag.
* configure.ac: When 'GUIX_LIBGCRYPT_LIBDIR' returns the empty string,
  set LIBGCRYPT_LIBDIR to "no".
* config-daemon.ac: Add missing space.

config-daemon.ac

@@ -51,7 +51,7 @@ if test "x$guix_build_daemon" = "xyes"; then
     no)
       LIBGCRYPT_LIBS="-lgcrypt"
       ;;
-   *)
+    *)
       LIBGCRYPT_LIBS="-L$LIBGCRYPT_LIBDIR -lgcrypt"
       ;;
   esac

configure.ac

@@ -169,6 +169,9 @@ case "x$LIBGCRYPT_PREFIX$LIBGCRYPT_LIBDIR" in
     GUIX_LIBGCRYPT_LIBDIR([LIBGCRYPT_LIBDIR])
     if test "x$LIBGCRYPT_LIBDIR" != x; then
       LIBGCRYPT="$LIBGCRYPT_LIBDIR/libgcrypt"
+    else
+      dnl 'config-daemon.ac' expects "no" in this case.
+      LIBGCRYPT_LIBDIR="no"
     fi
     ;;
 esac

m4/guix.m4

@@ -279,7 +279,7 @@ AC_DEFUN([GUIX_LIBGCRYPT_LIBDIR], [
   AC_CACHE_CHECK([libgcrypt's library directory],
     [guix_cv_libgcrypt_libdir],
     [if test "x$LIBGCRYPT_CONFIG" != "x"; then
-       guix_cv_libgcrypt_libdir=`$LIBGCRYPT_CONFIG --libs | sed -e "s/.*-L\([[^ ]]\+\)[[[:blank:]]]\+-lgcrypt.*/\1/g"`
+       guix_cv_libgcrypt_libdir=`$LIBGCRYPT_CONFIG --libs | grep -e -L | sed -e "s/.*-L\([[^ ]]\+\)[[[:blank:]]]\+-lgcrypt.*/\1/g"`
      else
        guix_cv_libgcrypt_libdir=""
      fi])