support/config-fragments: add RISC-V 64-bit to autobuild configs

Add a minimal RISC-V 64-bit autobuild configuration for the
internal toolchain with glibc.

Signed-off-by: Mark Corbin <mark.corbin@embecosm.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

support/config-fragments/autobuild/br-riscv64-internal-glibc.config

@@ -0,0 +1,2 @@
+BR2_riscv=y
+BR2_TOOLCHAIN_BUILDROOT_GLIBC=y

support/config-fragments/autobuild/toolchain-configs.csv

@@ -50,6 +50,7 @@ support/config-fragments/autobuild/br-powerpc64le-power8-glibc.config,x86_64
 support/config-fragments/autobuild/br-powerpc64-power7-glibc.config,x86_64
 support/config-fragments/autobuild/br-powerpc-e500mc-full.config,x86_64
 support/config-fragments/autobuild/br-powerpc-internal-full.config,any
+support/config-fragments/autobuild/br-riscv64-internal-glibc.config,any
 support/config-fragments/autobuild/br-sh4-full.config,x86_64
 support/config-fragments/autobuild/br-sparc-uclibc.config,x86_64
 support/config-fragments/autobuild/br-sparc64-glibc.config,x86_64