meson: Add LLVM bitcode emissions for contrib libraries

The libraries for which bitcode files are generated are selected
manually. Bitcode is only worthwhile for extensions that provide
lightweight SQL operators/functions that can benefit from being inlined
into JIT-compiled expressions, so this is restricted to citext, hstore,
intarray, ltree and pg_trgm.

Author: Andres Freund <andres@anarazel.de>
Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Author: Diego Fronza <diego.fronza@percona.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Diego Fronza <diego.fronza@percona.com>
Reviewed-by: Zsolt Parragi <zsolt.parragi@percona.com>
Discussion: https://postgr.es/m/206b001d-1884-4081-bd02-bed5c92f02ba%40eisentraut.org

Author: nbyavuz

contrib/citext/meson.build

@@ -30,6 +30,11 @@ install_data(
   kwargs: contrib_data_args,
 )
 
+bitcode_modules += {
+  'target': citext,
+  'srcfiles': citext_sources,
+}
+
 tests += {
   'name': 'citext',
   'sd': meson.current_source_dir(),

contrib/hstore/meson.build

@@ -43,6 +43,11 @@ install_headers(
   install_dir: dir_include_extension / 'hstore',
 )
 
+bitcode_modules += {
+  'target': hstore,
+  'srcfiles': hstore_sources,
+}
+
 tests += {
   'name': 'hstore',
   'sd': meson.current_source_dir(),

contrib/intarray/meson.build

@@ -33,6 +33,11 @@ install_data(
   kwargs: contrib_data_args,
 )
 
+bitcode_modules += {
+  'target': intarray,
+  'srcfiles': intarray_sources,
+}
+
 tests += {
   'name': 'intarray',
   'sd': meson.current_source_dir(),

contrib/ltree/meson.build

@@ -41,6 +41,15 @@ install_headers(
   install_dir: dir_include_extension / 'ltree',
 )
 
+ltree_dir = meson.current_source_dir()
+bitcode_modules += {
+  'target': ltree,
+  'srcfiles': ltree_sources,
+  'additional_flags': [
+    '-I@0@'.format(ltree_dir)
+  ]
+}
+
 tests += {
   'name': 'ltree',
   'sd': meson.current_source_dir(),

contrib/pg_trgm/meson.build

@@ -32,6 +32,11 @@ install_data(
   kwargs: contrib_data_args,
 )
 
+bitcode_modules += {
+  'target': pg_trgm,
+  'srcfiles': pg_trgm_sources,
+}
+
 tests += {
   'name': 'pg_trgm',
   'sd': meson.current_source_dir(),