populate_sdk: Add SDK toolchain language selection support

Add a new variable SDK_TOOLCHAIN_LANGS to allow different language support
to be selected within SDKs. Initially supported options are rust and go.

(From OE-Core rev: 0026b5687147410e4c7140ca5133089ebb51d9d4)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/populate_sdk_base.bbclass

@@ -43,9 +43,22 @@ B:task-populate-sdk = "${SDK_DIR}"
 
 SDKTARGETSYSROOT = "${SDKPATH}/sysroots/${REAL_MULTIMACH_TARGET_SYS}"
 
-TOOLCHAIN_HOST_TASK ?= "nativesdk-packagegroup-sdk-host packagegroup-cross-canadian-${MACHINE}"
+SDK_TOOLCHAIN_LANGS ??= ""
+SDK_TOOLCHAIN_LANGS:remove:mingw32 = "rust"
+
+TOOLCHAIN_HOST_TASK ?= " \
+    nativesdk-packagegroup-sdk-host \
+    packagegroup-cross-canadian-${MACHINE} \
+    ${@bb.utils.contains('SDK_TOOLCHAIN_LANGS', 'go', 'packagegroup-go-cross-canadian-${MACHINE}', '', d)} \
+    ${@bb.utils.contains('SDK_TOOLCHAIN_LANGS', 'rust', 'packagegroup-rust-cross-canadian-${MACHINE}', '', d)} \
+"
 TOOLCHAIN_HOST_TASK_ATTEMPTONLY ?= ""
-TOOLCHAIN_TARGET_TASK ?= "${@multilib_pkg_extend(d, 'packagegroup-core-standalone-sdk-target')} target-sdk-provides-dummy"
+TOOLCHAIN_TARGET_TASK ?= " \
+    ${@multilib_pkg_extend(d, 'packagegroup-core-standalone-sdk-target')} \
+    ${@bb.utils.contains('SDK_TOOLCHAIN_LANGS', 'go', multilib_pkg_extend(d, 'packagegroup-go-sdk-target'), '', d)} \
+    ${@bb.utils.contains('SDK_TOOLCHAIN_LANGS', 'rust', multilib_pkg_extend(d, 'libstd-rs'), '', d)} \
+    target-sdk-provides-dummy \
+"
 TOOLCHAIN_TARGET_TASK_ATTEMPTONLY ?= ""
 TOOLCHAIN_OUTPUTNAME ?= "${SDK_NAME}-toolchain-${SDK_VERSION}"