Handle *.export.libs, distinguish interface and implementation dependencies

A library dependency on another libraries is either "interface" or
"implementation". If it is interface, then everyone who links to this library
should also link to the interface dependency, explicitly. A good example of
an interface dependency is a library API that is called in inline functions.

Interface dependencies of a library should be explicitly listed in the
*.export.libs (where we can also list target names). So the typical usage
will be along these lines:

import int_libs = libfoo%lib{foo}
import int_libs += ...

import imp_libs = libbar%lib{bar}
import imp_libs += ...

lib{baz}: ... $int_libs $imp_libs

lib{baz}: cxx.export.libs = $int_libs

1 files changed, 2 insertions, 2 deletions

diff --git a/build2/cc/compile.cxx b/build2/cc/compile.cxx
index 58dbe30..56122e8 100644
--- a/build2/cc/compile.cxx
+++ b/build2/cc/compile.cxx
@@ -882,8 +882,8 @@ namespace build2
           else
           {
             // Note that we skip any target type-specific searches (like for
-            // an existing file) and go straight for the target make since we
-            // need to find the target explicitly spelled out.
+            // an existing file) and go straight for the target object since
+            // we need to find the target explicitly spelled out.
             //
             auto i (targets.find (*tt, d, out, n, e, trace));
             r = i != targets.end () ? i->get () : nullptr;