Build openpower-libhei as a static library

Build a static library that can be linked to by other applications.

Signed-off-by: Ben Tyner <ben.tyner@ibm.com>
Change-Id: I4dec91928381712674e6621792830f811c44c30d
diff --git a/test/meson.build b/test/meson.build
index ce1e5da..209bad3 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -2,7 +2,8 @@
 subdir('simulator')
 
 # supporting files that need compiled/linked
-test_src = ['../src/util/hei_bit_string.cpp']
+test_src = ['../src/util/hei_bit_string.cpp',
+               'hei_user_defines.cpp']
 
 # build g-test framework unit tests
 gtests = [