package/frr: fix detection of host-python3

package/frr: fix detection of host-python3

Add an upstream patch to fix detection of host-python3 and avoid the
following failure because of missing --embed flag:

configure:22276: checking python interpreter python3
configure:22278: "$PYTHON" -c 'import sys; open("conftest.pyver", "w").write(sys.executable or ""); sys.exit(not (sys.version_info.major == 2 and sys.version_info.minor >= 7))'
configure:22281: $? = 1
configure:22287: "$PYTHON" -c 'import sys; open("conftest.pyver", "w").write(sys.executable or ""); sys.exit(not ((sys.version_info.major == 3 and sys.version_info.minor >= 2) or sys.version_info.major > 3))'
configure:22290: $? = 0
configure:22310: result: /home/buildroot/autobuild/run/instance-1/output-1/host/bin/python3 (python3)
py_abi= py_ldver=3.9 py_ver=3.9 py_bindir=/home/buildroot/autobuild/run/instance-1/output-1/host/bin/
configure:22326: checking whether /home/buildroot/autobuild/run/instance-1/output-1/host/bin/python3.9-config is available
configure:22329: result: yes
configure:22339: checking whether /home/buildroot/autobuild/run/instance-1/output-1/host/bin/python3.9-config provides a working build environment
configure:22376: /usr/bin/gcc -std=gnu11 -o conftest -O2 -I/home/buildroot/autobuild/run/instance-1/output-1/host/include -fno-omit-frame-pointer -funwind-tables -Wall -Wextra -Wmissing-prototypes -Wmissing-declarations -Wpointer-arith -Wbad-function-cast -Wwrite-strings -Wundef -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -pthread -I/home/buildroot/autobuild/run/instance-1/output-1/host/include/python3.9 -I/home/buildroot/autobuild/run/instance-1/output-1/host/include/python3.9 -I/home/buildroot/autobuild/run/instance-1/output-1/host/include -L/home/buildroot/autobuild/run/instance-1/output-1/host/lib -Wl,-rpath,/home/buildroot/autobuild/run/instance-1/output-1/host/lib conftest.c    -L/home/buildroot/autobuild/run/instance-1/output-1/host/lib  -lcrypt -lpthread -ldl  -lutil -lm -lm  >&5
/tmp/ccrVSMCb.o: In function `main':
conftest.c:(.text.startup+0x5): undefined reference to `Py_Initialize'

Fixes:
 - http://autobuild.buildroot.org/results/d33293bfb2f8d558efa2d83e5cb71226d3e65c7f

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>