meson: add option to allow override default default_pkcs11_module

[embetrix]

fix #510

[simo5]

Some changes are needed

[embetrix]

I tested all combinations:

meson setup builddir 
meson setup builddir -Ddefault_pkcs11_module=""
meson setup builddir -Ddefault_pkcs11_module=/opt/path/mymod.so

Possible configs:

builddir/config.h:#define DEFAULT_PKCS11_MODULE "/usr/lib/x86_64-linux-gnu/p11-kit-proxy.so"
builddir/config.h:#define DEFAULT_PKCS11_MODULE "/usr/lib/x86_64-linux-gnu/p11-kit-proxy.so"
builddir/config.h:#define DEFAULT_PKCS11_MODULE "/opt/path/mymod.so"

[simo5]

LGTM

[embetrix]

@simo5 looks like libp11-kit-dev dependency is missing in the CI

[simo5]

@simo5 looks like libp11-kit-dev dependency is missing in the CI

It may have been intentional, we do support building w/o p11-kit-dev ... in which case no default would be present so now that I think of it I guess we need to allow for no defaults

[simo5]

Indeed we do support it not being defined:

pkcs11-provider/src/interface.c

Line 234 in 2ef2402

#ifdef DEFAULT_PKCS11_MODULE

So I guess we need to allow an undefined defult, I guess the code needs to be:

if default_pkcs11_module != ''
  conf.set_quoted('DEFAULT_PKCS11_MODULE', default_pkcs11_module)
endif

And leave the CI with default undefined (ie revert the change to add p11-kit-dev)

[embetrix]

@simo5: done

[simo5]

Lately MacOS CI is flakier and times out, I tried to respin it and timed out again, so I am just going to ignore it for now.
Thanks for the speedy contribution.