linkers: Add a PosixDynamicLinkerMixin

This is a mixin class for DynamicLinkers that aims to provide only the
most basic posix-like linker arguments, in other words bits that gnu ld,
apple's ld, solaris's ld, and other completely disjoint linkers that are
used on Unix-like OSes share.

mesonbuild/linkers.py

@@ -349,3 +349,22 @@ class DynamicLinker(metaclass=abc.ABCMeta):
                          rpath_paths: str, build_rpath: str,
                          install_rpath: str) -> typing.List[str]:
         return []
+
+
+class PosixDynamicLinkerMixin:
+
+    """Mixin class for POSIX-ish linkers.
+
+    This is obviously a pretty small subset of the linker interface, but
+    enough dynamic linkers that meson supports are POSIX-like but not
+    GNU-like that it makes sense to split this out.
+    """
+
+    def get_output_args(self, outname: str) -> typing.List[str]:
+        return ['-o', outname]
+
+    def get_std_shared_lib_args(self) -> typing.List[str]:
+        return ['-shared']
+
+    def get_search_args(self, dirname: str) -> typing.List[str]:
+        return ['-L', dirname]