the final vmlinux stripped off debugging information

After a clean build of the system, there's no .debug_line and friends among the sections. This renders the vmlinux file crippled in terms of debugging.

piosze01@e102518-lin:/work/vexpress_linaro_19.09_lsk_android/android
$ arm-linux-androideabi-readelf --sections out/target/product/vexpress/obj/kernel/vmlinux
There are 31 section headers, starting at offset 0x649d34:

Section Headers:
  [Nr] Name Type Addr Off Size ES Flg Lk Inf Al
  [ 0] NULL 00000000 000000 000000 00 0 0 0
  [ 1] .head.text PROGBITS c0008000 008000 000260 00 AX 0 0 32
  [ 2] .text PROGBITS c0008280 008280 3e52fc 00 AX 0 0 64
  [ 3] .rodata PROGBITS c03ee000 3ee000 166a94 00 A 0 0 256
  [ 4] __bug_table PROGBITS c0554a98 554a98 008d84 00 A 0 0 1
  [ 5] __ksymtab PROGBITS c055d81c 55d81c 006930 00 A 0 0 4
  [ 6] __ksymtab_gpl PROGBITS c056414c 56414c 004648 00 A 0 0 4
  [ 7] __ksymtab_strings PROGBITS c0568794 568794 018cb4 00 A 0 0 1
  [ 8] __param PROGBITS c0581448 581448 0009f0 00 A 0 0 4
  [ 9] __modver PROGBITS c0581e38 581e38 0001c8 00 A 0 0 4
  [10] __ex_table PROGBITS c0582000 582000 000f10 00 A 0 0 8
  [11] .ARM.unwind_idx ARM_EXIDX c0582f10 582f10 0267d8 00 AL 16 0 4
  [12] .ARM.unwind_tab PROGBITS c05a96e8 5a96e8 002a78 00 A 0 0 4
  [13] .notes NOTE c05ac160 5ac160 000024 00 AX 0 0 4
  [14] .vectors PROGBITS 00000000 5b0000 000020 00 AX 0 0 2
  [15] .stubs PROGBITS 00001000 5b1000 000240 00 AX 0 0 32
  [16] .init.text PROGBITS c05ad260 5b5260 0271dc 00 AX 0 0 32
  [17] .exit.text PROGBITS c05d443c 5dc43c 0010f0 00 AX 0 0 4
  [18] .init.arch.info PROGBITS c05d552c 5dd52c 0000f0 00 A 0 0 4
  [19] .init.tagtable PROGBITS c05d561c 5dd61c 000048 00 A 0 0 4
  [20] .init.smpalt PROGBITS c05d5664 5dd664 007a80 00 A 0 0 4
  [21] .init.pv_table PROGBITS c05dd0e4 5e50e4 00035c 00 A 0 0 1
  [22] .init.data PROGBITS c05dd440 5e5440 01d81c 00 WA 0 0 8
  [23] .data..percpu PROGBITS c05fb000 603000 003600 00 WA 0 0 64
  [24] .data PROGBITS c0600000 608000 041b90 00 WA 0 0 64
  [25] .bss NOBITS c0641c00 649b90 06ac7c 00 WA 0 0 256
  [26] .comment PROGBITS 00000000 649b90 00003a 01 MS 0 0 1
  [27] .ARM.attributes ARM_ATTRIBUTES 00000000 649bca 00002b 00 0 0 1
  [28] .shstrtab STRTAB 00000000 649bf5 00013f 00 0 0 1
  [29] .symtab SYMTAB 00000000 64a20c 14adb0 10 30 71702 4
  [30] .strtab STRTAB 00000000 794fbc 0fff43 00 0 0 1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)