package/alchemy: add host-pkgconf dependency

host-pkgconf is a mandatory dependency since the addition of the package
in commit 7f1f3f87868fa333833dbba9f4f07adc338b34ed resulting in the
following ulog build failure:

/home/buildroot/autobuild/run/instance-0/output-1/per-package/ulog/host/opt/alchemy/check.mk:36: *** 'pkg-config' is required.  Stop.

An other option would be to set TARGET_OS to baremetal but it could have
unexpected side-effects such as removing -fPIC for arm targets

Fixes:
 - http://autobuild.buildroot.org/results/c731fe0e9bdbfce0823f9c48641f1ed710fa6125

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Reviewed-by: Romain Naour <romain.naour@gmail.com>
Reviewed-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/alchemy/alchemy.mk

@@ -8,7 +8,7 @@ ALCHEMY_VERSION = d95b3c38cd37814a1b98d0bbf813de7adaaecfbc
 ALCHEMY_SITE = $(call github,Parrot-Developers,alchemy,$(ALCHEMY_VERSION))
 ALCHEMY_LICENSE = BSD-3-Clause (Alchemy), GPL-2.0 (kconfig)
 ALCHEMY_LICENSE_FILES = COPYING README
-HOST_ALCHEMY_DEPENDENCIES = host-python3
+HOST_ALCHEMY_DEPENDENCIES = host-pkgconf host-python3
 
 ALCHEMY_HOME = $(HOST_DIR)/opt/alchemy
 ALCHEMY_SDK_BASEDIR = $(STAGING_DIR)/usr/lib/alchemy/sdk
@@ -35,6 +35,7 @@ ALCHEMY_TARGET_ENV = \
 	ALCHEMY_HOME=$(ALCHEMY_HOME) \
 	ALCHEMY_WORKSPACE_DIR="$(@D)" \
 	ALCHEMY_TARGET_OUT=alchemy-out \
+	PKGCONFIG_BIN=$(PKG_CONFIG_HOST_BINARY) \
 	TARGET_OS=linux \
 	TARGET_OS_FLAVOUR=buildroot \
 	TARGET_CROSS="$(TARGET_CROSS)" \