support armv7 in tripple mappings (#1116)

diff --git a/rust/platform/triple_mappings.bzl b/rust/platform/triple_mappings.bzl
index 1915ea4..f7d42cb 100644
--- a/rust/platform/triple_mappings.bzl
+++ b/rust/platform/triple_mappings.bzl
@@ -23,6 +23,7 @@
     "aarch64-linux-android",
     "aarch64-unknown-linux-gnu",
     "arm-unknown-linux-gnueabi",
+    "armv7-unknown-linux-gnueabi",
     "i686-linux-android",
     "i686-unknown-freebsd",
     "powerpc-unknown-linux-gnu",