This was wrong since commit
c360ceea4deb5d56c94126e31b9614734e8c1a7e.
Also fix incorrect indentation (tab instead of spaces).
Found using hermetic builds with Nix:
https://github.com/NixOS/nixpkgs/pull/54398#discussion_r280125735
gsm_dep = cc.find_library('gsm', required : get_option('gsm'))
have_gsm_create = cc.has_header_symbol('gsm.h', 'gsm_create')
if not have_gsm_create
- have_gsm_create = cc.has_header_symbol('gsm/smg.h', 'gsm_create')
+ have_gsm_create = cc.has_header_symbol('gsm/gsm.h', 'gsm_create')
if not have_gsm_create and get_option('gsm').enabled()
error('GSM plugin is enabled: found libgsm but no headers')
else