boot/barebox: add optional dependencies on host-openssl and host-libusb

Some barebox targets need to build host tools (for example rockchip64
uses scripts/rkimage) that require some host libraries, such as
host-openssl or host-libusb. These are detected by the Barebox build
system using pkg-config.

In order to allow supporting such Barebox configurations, we add two
new options: BR2_TARGET_BAREBOX_NEEDS_OPENSSL and
BR2_TARGET_BAREBOX_NEEDS_LIBUSB that respectively allow to ensure that
host-openssl and/or host-libusb are built before Barebox.

Additionally, $(1)_MAKE_ENV is adjusted to ensure that when pkg-config
is run by the Barebox build system, it finds host libraries. This is
similar to what is done in U-Boot.

This allows to fix the following build failure:

  HOSTCC  scripts/rkimage
Package openssl was not found in the pkg-config search path.
Perhaps you should add the directory containing `openssl.pc'
to the PKG_CONFIG_PATH environment variable
Package 'openssl', required by 'virtual:world', not found
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: /tmp/ccN8Xyaj.o: in function `main':
rkimage.c:(.text.startup+0x218): undefined reference to `SHA256_Init'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: rkimage.c:(.text.startup+0x22b): undefined reference to `SHA256_Update'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: rkimage.c:(.text.startup+0x23e): undefined reference to `SHA256_Final'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: rkimage.c:(.text.startup+0x253): undefined reference to `SHA256_Init'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: rkimage.c:(.text.startup+0x265): undefined reference to `SHA256_Update'
/usr/lib/gcc/x86_64-pc-linux-gnu/12/../../../../x86_64-pc-linux-gnu/bin/ld: rkimage.c:(.text.startup+0x275): undefined reference to `SHA256_Final'
collect2: error: ld returned 1 exit status
make[2]: *** [scripts/Makefile.host:107: scripts/rkimage] Error 1
make[1]: *** [Makefile:976: scripts] Error 2

Signed-off-by: Alexander Shiyan <eagle.alexander923@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

boot/barebox/Config.in

@@ -54,6 +54,18 @@ config BR2_TARGET_BAREBOX_CUSTOM_PATCH_DIR
 
 	  Most users may leave this empty
 
+config BR2_TARGET_BAREBOX_NEEDS_OPENSSL
+	bool "Barebox needs OpenSSL"
+	help
+	  Select this option if your Barebox board configuration
+	  requires OpenSSL to be available on the host.
+
+config BR2_TARGET_BAREBOX_NEEDS_LIBUSB
+	bool "Barebox needs LibUSB"
+	help
+	  Select this option if your Barebox board configuration
+	  requires libUSB to be available on the host.
+
 if BR2_TARGET_BAREBOX_CUSTOM_GIT
 
 config BR2_TARGET_BAREBOX_CUSTOM_GIT_REPO_URL

boot/barebox/barebox.mk

@@ -43,6 +43,14 @@ ifeq ($(BR2_TARGET_BAREBOX_LATEST_VERSION),y)
 $(1)_LICENSE_FILES = COPYING
 endif
 
+ifeq ($(BR2_TARGET_BAREBOX_NEEDS_OPENSSL),y)
+BAREBOX_DEPENDENCIES += host-openssl host-pkgconf
+endif
+
+ifeq ($(BR2_TARGET_BAREBOX_NEEDS_LIBUSB),y)
+BAREBOX_DEPENDENCIES += host-libusb host-pkgconf
+endif
+
 $(1)_CUSTOM_EMBEDDED_ENV_PATH = $$(call qstrip,$$(BR2_TARGET_$(1)_CUSTOM_EMBEDDED_ENV_PATH))
 
 ifneq ($$(call qstrip,$$(BR2_TARGET_BAREBOX_CUSTOM_PATCH_DIR)),)
@@ -73,6 +81,12 @@ endif
 
 $(1)_MAKE_FLAGS = ARCH=$$($(1)_ARCH) CROSS_COMPILE="$$(TARGET_CROSS)"
 $(1)_MAKE_ENV = $$(TARGET_MAKE_ENV)
+$(1)_MAKE_ENV += \
+	PKG_CONFIG="$(PKG_CONFIG_HOST_BINARY)" \
+	PKG_CONFIG_SYSROOT_DIR="/" \
+	PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 \
+	PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 \
+	PKG_CONFIG_LIBDIR="$(HOST_DIR)/lib/pkgconfig:$(HOST_DIR)/share/pkgconfig"
 
 ifeq ($$(BR2_REPRODUCIBLE),y)
 $(1)_MAKE_ENV += \