support/testing: build a glibc toolchain for docker / docker-compose tests

runc (which is a reverse dependency of docker-engine) is about to gain a
!uclibc dependency, so move to a glibc toolchain instead.

There are currently no prebuilt x86_64 / core2 / glibc toolchains available,
so instead use the internal toolchain backend to build one.

While we are at it, drop the infra.basetest.BASIC_TOOLCHAIN_CONFIG
reference, as that ARM toolchain configuration doesn't make any sense for
this x86-64 based test.

add docker / docker-compose tests

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

support/testing/tests/package/test_docker_compose.py

@@ -4,19 +4,12 @@ import infra.basetest
 
 
 class TestDockerCompose(infra.basetest.BRTest):
-    config = infra.basetest.BASIC_TOOLCHAIN_CONFIG + \
+    config = \
         """
         BR2_x86_64=y
         BR2_x86_core2=y
-        BR2_TOOLCHAIN_EXTERNAL=y
-        BR2_TOOLCHAIN_EXTERNAL_CUSTOM=y
-        BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
-        BR2_TOOLCHAIN_EXTERNAL_URL="http://autobuild.buildroot.org/toolchains/tarballs/br-x86-64-core2-full-2018.05.tar.bz2"
-        BR2_TOOLCHAIN_EXTERNAL_GCC_6=y
-        BR2_TOOLCHAIN_EXTERNAL_HEADERS_4_16=y
-        BR2_TOOLCHAIN_EXTERNAL_LOCALE=y
-        # BR2_TOOLCHAIN_EXTERNAL_HAS_THREADS_DEBUG is not set
-        BR2_TOOLCHAIN_EXTERNAL_CXX=y
+        BR2_TOOLCHAIN_BUILDROOT_GLIBC=y
+        BR2_KERNEL_HEADERS_4_19=y
         BR2_SYSTEM_DHCP="eth0"
         BR2_ROOTFS_POST_BUILD_SCRIPT="{}"
         BR2_ROOTFS_POST_SCRIPT_ARGS="{}"