tools: make libressl build depend on pkg-config

Ensure that pkg-config is available before building libressl as we're going
to need it for setting proper link flags in utilities requiring libcrypto.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

tools/Makefile

@@ -70,6 +70,7 @@ $(curdir)/findutils/compile := $(curdir)/bison/install
 $(curdir)/gengetopt/compile := $(curdir)/libtool/install
 $(curdir)/patchelf/compile := $(curdir)/libtool/install
 $(curdir)/dosfstools/compile := $(curdir)/autoconf/install $(curdir)/automake/install
+$(curdir)/libressl/compile := $(curdir)/pkg-config/install
 $(curdir)/mkimage/compile += $(curdir)/libressl/install
 $(curdir)/firmware-utils/compile += $(curdir)/libressl/install
 $(curdir)/cmake/compile += $(curdir)/libressl/install