mpfr: add explicit dependencies for host variant

Signed-off-by: Julien Floret <julien.floret@6wind.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/mpfr/mpfr.mk

@@ -11,6 +11,7 @@ MPFR_LICENSE = LGPLv3+
 MPFR_LICENSE_FILES = COPYING.LESSER
 MPFR_INSTALL_STAGING = YES
 MPFR_DEPENDENCIES = gmp
+HOST_MPFR_DEPENDENCIES = host-gmp
 MPFR_MAKE_OPTS = RANLIB=$(TARGET_RANLIB)
 
 $(eval $(autotools-package))