Enable PSVita (arm-none-eabi) compile again and add it to CI (#594)

diff --git a/src/hb-open-file-private.hh b/src/hb-open-file-private.hh
index a6d5a6b..741e74c 100644
--- a/src/hb-open-file-private.hh
+++ b/src/hb-open-file-private.hh
@@ -90,7 +90,7 @@
       if (start_offset >= tables.len)
         *table_count = 0;
       else
-        *table_count = MIN (*table_count, tables.len - start_offset);
+        *table_count = MIN<unsigned int> (*table_count, tables.len - start_offset);
 
       const TableRecord *sub_tables = tables.array + start_offset;
       unsigned int count = *table_count;