grub-emu fails to build from source on 32-bit PowerPC due to PKS support

[glaubitz]

Trying to build GRUB on 32-bit PowerPC fails when build with --with-platform=emu with:

/usr/bin/ld: appendedsig.module: in function `grub_mod_init':
/home/glaubitz/grub/grub-core/commands/appendedsig/appendedsig.c:1615:(.text+0x2ab4):
 undefined reference to `grub_pks_get_keystore'
/usr/bin/ld: appendedsig.module: in function `create_dbs_from_pks':
/home/glaubitz/grub/grub-core/commands/appendedsig/appendedsig.c:1400:(.text+0x2c3c):
 undefined reference to `grub_pks_free_data'
collect2: error: ld returned 1 exit status

See this upstream report here: https://lists.gnu.org/archive/html/grub-devel/2026-02/msg00077.html