configs: microblazeel-zephyr-elf: Disable Picolibc

This commit disables Picolibc for the microblazeel-zephyr-elf toolchain
because Picolibc currently fails to build for the Microblaze
architecture (see GitHub issue #639).

Revert this commit when #639 is fixed.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

Author: stephanosio

configs/microblazeel-zephyr-elf.config

@@ -5,3 +5,6 @@ CT_ARCH_LE=y
 CT_TARGET_CFLAGS="-G0 -fno-pic"
 CT_TARGET_VENDOR="zephyr"
 CT_MULTILIB=y
+# FIXME: Picolibc is disabled for microblazeel due to build failure
+#        (see GitHub issue #639).
+CT_COMP_LIBS_PICOLIBC=n