libbej: Export the package for other repo to use

Make the library non-static so that other repo can be linked to
it. Also install the headers for libbej.

Change-Id: I89dba36859b569283b61d3ac448f23289c21944a
Signed-off-by: Willy Tu <wltu@google.com>
diff --git a/meson.build b/meson.build
index dc88a95..bb7c166 100644
--- a/meson.build
+++ b/meson.build
@@ -14,6 +14,8 @@
 
 libbej_incs = include_directories('include')
 subdir('src')
+subdir('include')
 if not get_option('tests').disabled()
   subdir('test')
 endif
+