ci: add build/unit-test coverage for armv7 (#42386)

arm64 hosts support running armv7 (armhf) binaries, so we can
cross compile and run the unit tests without performance issues.

armv7 (armhf) is a primary architecture on Ubuntu, so build
regressions block new version updates, and adding coverage
helps to avoid introducing regressions.

src/test/meson.build

@@ -547,6 +547,7 @@ executables += [
         core_test_template + {
                 'sources' : files('test-execute.c'),
                 'dependencies' : common_test_dependencies,
+                'type' : meson.is_cross_build() ? 'manual' : '',
                 'timeout' : 360,
         },
         core_test_template + {

src/test/test-crypto-util.c

@@ -129,7 +129,7 @@ static const struct {
 };
 
 TEST(digest_size) {
-        size_t size;
+        size_t size = 0;  /* avoid false maybe-uninitialized warning */
 
         FOREACH_ELEMENT(t, digest_size_table) {
                 assert(openssl_digest_size(t->alg, &size) >= 0);