Automatically run ldconfig after install if possible.

c++/Makefile.am

@@ -227,8 +227,13 @@ capnpc_c___SOURCES = src/capnp/compiler/capnpc-c++.c++
 
 # Symlink capnpc -> capnp.  The capnp binary will behave like the old capnpc
 # binary (i.e. like "capnp compile") when invoked via this symlink.
+#
+# Also attempt to run ldconfig, because otherwise users get confused.  If
+# it fails (e.g. because the platform doesn't have it, or because the
+# user doesn't have root privileges), don't worry about it.
 install-exec-hook:
 	ln -sf capnp $(DESTDIR)$(bindir)/capnpc
+	ldconfig < /dev/null > /dev/null 2>&1 || true
 
 uninstall-hook:
 	rm -f $(DESTDIR)$(bindir)/capnpc

doc/install.md

@@ -67,9 +67,6 @@ This will install `capnp`, the Cap'n Proto command-line tool.  It will also inst
 `libcapnpc`, and `libkj` in `/usr/local/lib` and headers in `/usr/local/include/capnp` and
 `/usr/local/include/kj`.
 
-On Linux, if running `capnp` immediately after installation produces an error complaining about
-missing libraries, run `sudo ldconfig` and try again.
-
 ### Building from Git with Autotools
 
 If you download directly from Git, and you don't want to