framework: add new variable PKGCONFIG_BASE

[tcberner]

Summary

The base system started to provide certain pkgconfig files for
components it provides. This new variable allows ports to prefer base
copmonents explicitely using for example

PKGCONFIG_BASE=foo

This will create a symlingk of /usr/libdata/pkgconfig/foo.pc to
${WKRDIR}/.pkgconfig and adding said path to pkgconfigs search path.

This allows us to switch easily between base and port implementation
of different components (say openssl) by simply defining the appropriate
variable in (say ssl.mk).

[bapt]

Mk/bsd.port.mk

1688

Here that should be PKG_CONFIGi_DIR=${PKG_CONFIG_LINKDIR}:${LOCALBASE}/libdata/pkgconfig

5162

I don't think the realpath call is necessary here.

[tcberner]

Mk/bsd.port.mk

5162

this was added, as some pc files are symlinks

[tcberner]

• document realpath usage
• append default path to environment

[bapt]

Mk/bsd.port.mk

1688

the real variable is PKG_CONFIG_LIBDIR

5162

RLN will expand to install -l rs, which in case of a symlink or symlink will to do the path expansion, so I stand by my the realpath call is not useful:

bapt@lappy:~ $ readlink /usr/libdata/pkgconfig/menu.pc
menuw.pc
bapt@lappy:~ $ install -l rs /usr/libdata/pkgconfig/menu.pc ./bla
bapt@lappy:~ $ readlink bla
../../libdata/pkgconfig/menuw.pc

[tcberner]

• Use proper pkg-config environment variable
• Remove unnecessary realpath useage, which install (RLN) already handles
• Also append /usr/libdata/pkgconfig to the environment

[tcberner]

• Use proper pkg-config environment variable
• Remove unnecessary realpath useage, which install (RLN) already handles
• Also append /usr/libdata/pkgconfig to the environment