Declare GDB client

Author: ivankravets

builder/main.py

@@ -54,6 +54,7 @@ def _get_board_f_flash(env):
     AS="xtensa-lx106-elf-as",
     CC="xtensa-lx106-elf-gcc",
     CXX="xtensa-lx106-elf-g++",
+    GDB="xtensa-lx106-elf-gdb",
     OBJCOPY="esptool",
     RANLIB="xtensa-lx106-elf-ranlib",
     SIZETOOL="xtensa-lx106-elf-size",