Quote the default pkgconfigdir

The second argument to AC_SUBST is placed on the right-hand-side of a
shell variable assignment.  Without the single quotes, ${libdir} is
expanded when that variable assignment is executed, which is earlier
than we want.

Author: turboencabulator

configure.ac

@@ -342,7 +342,7 @@ AM_CONDITIONAL([BLACS], [false])
 AM_CONDITIONAL([ICB], [test x"$enable_icb" != x"no"])
 AM_CONDITIONAL([EIGEN], [test x"$enable_eigen" != x"no"])
 
-m4_ifdef([PKG_INSTALLDIR], [PKG_INSTALLDIR], [AC_SUBST([pkgconfigdir], [${libdir}/pkgconfig])])
+m4_ifdef([PKG_INSTALLDIR], [PKG_INSTALLDIR], [AC_SUBST([pkgconfigdir], ['${libdir}/pkgconfig'])])
 AC_SUBST([ARPACK_PC_LIBS_PRIVATE], ["$LAPACK_LIBS $BLAS_LIBS"])
 AC_SUBST([PARPACK_PC_LIBS_PRIVATE], ["$LAPACK_LIBS $BLAS_LIBS $MPI_Fortran_LIBS"])