build.info: Introduce special syntax for dependencies on script modules

build.info: Introduce special syntax for dependencies on script modules

The DEPEND statement, when applied on files generated with GENERATE, may
be used to specify script modules that the template to be generated from
depends on.  In short, this sort of depend:

    DEPEND[generated]=util/perl/OpenSSL/something.pm

... would generate a perl run that has the inclusion directory
'util/perl/OpenSSL' and 'something' as the module to be loaded.  However,
the package name for this module is 'OpenSSL::something', so to load it the
way it's expected, the inclusion directory should be 'util/perl', and the
module to be loaded should be specified as 'OpenSSL/something' (to be
massaged into a proper module name by the build file template).

To allow this, we introduce a file syntax, where a single '|' is used as a
directory separator, to delineate what part should be used as the inclustion
directory, and which part the module name to be loaded should be derived
from:

    DEPEND[generated]=util/perl|OpenSSL/something.pm

Fixes #21112

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21117)