meson: Improve PG_VERSION_STR generation

Previously the host operating system and 32/64 bit were not included and the
build machine's cpu was used, which is potentially wrong for cross builds.

Author: Juan José Santamaría Flecha <juanjo.santamaria@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CAC+AXB16gwYhKCdS+t0pk3U7kKtpVj5L-ynmhK3Gbea330At3w@mail.gmail.com

meson.build

@@ -143,12 +143,11 @@ cdata.set_quoted('PACKAGE_TARNAME', 'postgresql')
 
 pg_version += get_option('extra_version')
 cdata.set_quoted('PG_VERSION', pg_version)
-cdata.set_quoted('PG_VERSION_STR', 'PostgreSQL @0@ on @1@, compiled by @2@-@3@'.format(
-  pg_version, build_machine.cpu_family(), cc.get_id(), cc.version()))
 cdata.set_quoted('PG_MAJORVERSION', pg_version_major.to_string())
 cdata.set('PG_MAJORVERSION_NUM', pg_version_major)
 cdata.set('PG_MINORVERSION_NUM', pg_version_minor)
 cdata.set('PG_VERSION_NUM', pg_version_num)
+# PG_VERSION_STR is built later, it depends compiler test results
 cdata.set_quoted('CONFIGURE_ARGS', '')
 
 
@@ -2453,6 +2452,15 @@ cdata.set('MEMSET_LOOP_LIMIT', memset_loop_limit)
 cdata.set_quoted('DLSUFFIX', dlsuffix)
 
 
+# built later than the rest of the version metadata, we need SIZEOF_VOID_P
+cdata.set_quoted('PG_VERSION_STR',
+  'PostgreSQL @0@ on @1@-@2@, compiled by @3@-@4@, @5@-bit'.format(
+    pg_version, host_machine.cpu_family(), host_system,
+    cc.get_id(), cc.version(), cdata.get('SIZEOF_VOID_P') * 8,
+  )
+)
+
+
 
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 # Threading