firefox: Use system-wide nss & nspr
firefox: Use system-wide nss & nspr

The recipe requires system-wide nss & nspr but they were not used
because built-in libraries were implicitly enabled. This patch fix
this issue.

Firefox 45ESR requires following versions:

* nss: 3.21.1
* nspr: 4.12

You need krogoth or later to satisfy these version.

Signed-off-by: Takuro Ashie <71accf686b9a6e0fd369c5e62393a338d58863cd@clear-code.com>

kraj/meta-browser,shr-distribution/meta-browser,shr-distribution/meta-browser,twoerner/meta-browser,OSSystems/meta-browser,OSSystems/meta-browser,schnitzeltony/meta-browser,webdino/meta-browser,kraj/meta-browser,schnitzeltony/meta-browser,twoerner/meta-browser,OSSystems/meta-browser,kraj/meta-browser,webdino/meta-browser,twoerner/meta-browser,webdino/meta-browser,shr-distribution/meta-browser,shr-distribution/meta-browser,kraj/meta-browser,webdino/meta-browser,schnitzeltony/meta-browser,webdino/meta-browser,schnitzeltony/meta-browser,twoerner/meta-browser,OSSystems/meta-browser