make installation directory accessible by other projects

[egiovan]

By default the command fpm install will install the program and the library in $HOME/.local.
Sure, one have to set in fpm.toml:

[install]
library = true

I think it would be nice if another project could be able to access this installed library just by setting:

[build]
link = "my_library"
external-modules = "my_library"

Sure, one can use LIBRARY_PATH for the library or CPATH for the modules (but not with gfortran...).
But I think that it would be nice if it is done automatically, may be, with another option on the build section of the fpm.toml like:
use_installed_libraries = true