utils/genrandconfig: fix checking host glibc version

Unless explicitly told otherwise, subprocess.check_output() returns
bytes objects [0].

When we try to check the C library version (to check the Linaro
toolchain is usable), genrandconfig currently fails with:
    TypeError: cannot use a string pattern on a bytes-like object

So, as suggested in the python documentation, decocde() the output of
subprocess.check_output() before we can use it.

[0] https://docs.python.org/3/library/subprocess.html#subprocess.check_output

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

utils/genrandconfig

@@ -181,7 +181,7 @@ def is_toolchain_usable(configfile, config):
            'BR2_TOOLCHAIN_EXTERNAL_LINARO_AARCH64_BE=y\n' in configlines or \
            'BR2_TOOLCHAIN_EXTERNAL_LINARO_ARMEB=y\n' in configlines:
             ldd_version_output = subprocess.check_output(['ldd', '--version'])
-            glibc_version = ldd_version_output.splitlines()[0].split()[-1]
+            glibc_version = ldd_version_output.decode().splitlines()[0].split()[-1]
             if StrictVersion('2.14') > StrictVersion(glibc_version):
                 print("WARN: ignoring the Linaro ARM toolchains because too old host glibc", file=sys.stderr)
                 return False