When building against software that is being built uninstalled,
pkg-config returns values from the -uninstalled.pc variant which
might contain .la files as --libs.
This patch opens the .la files to figure out where the actual shared
library are.
Some part of this is inspired by what is done in the
gobject-introspection giscanner/utils.py code
Addition (+), subtraction (-), multiplication (*) and division (/) for numbers
follows the BIDMAS rules.
Strings and arrays can be concatenated with the addition operator
Strings can be concatenated with numbers with the addition operator