contrib: Update Linux build script to use Python 3.10

This commit updates the local Linux build script to link gdb-py against
Python 3.10, as done by the CI workflow.

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

contrib/linux_build_toolchain.sh

@@ -119,7 +119,7 @@ CT_LOG_EXTRA=y
 CT_LOG_LEVEL_MAX="EXTRA"
 CT_GDB_CROSS_PYTHON=y
 CT_GDB_CROSS_PYTHON_VARIANT=y
-CT_GDB_CROSS_PYTHON_BINARY="python3.8"
+CT_GDB_CROSS_PYTHON_BINARY="python3.10"
 CT_EXPERIMENTAL=y
 CT_ALLOW_BUILD_AS_ROOT=y
 CT_ALLOW_BUILD_AS_ROOT_SURE=y