update environment variable handling for pinning (#1573)

private/extensions/maven.bzl

diff --git a/private/extensions/maven.bzl b/private/extensions/maven.bzl
index 2ea955b..3ec6618 100644
--- a/private/extensions/maven.bzl
+++ b/private/extensions/maven.bzl
@@ -604,7 +604,7 @@
     # Second pass: merge and deduplicate repositories
     all_repo_names = {name: True for name in root_module_repos.keys() + non_root_module_repos.keys()}.keys()
 
-    repin_env_var = mctx.getenv("REPIN")
+    repin_env_var = mctx.getenv("REPIN") or mctx.getenv("RULES_JVM_EXTERNAL_REPIN")
     rje_verbose_env_var = mctx.getenv("RJE_VERBOSE")
 
     for repo_name in all_repo_names:
@@ -861,4 +861,5 @@
         "install": install,
         "override": override,
     },
+    environ = ["REPIN", "RULES_JVM_EXTERNAL_REPIN", "RJE_VERBOSE"],
 )

private/rules/coursier.bzl

diff --git a/private/rules/coursier.bzl b/private/rules/coursier.bzl
index ba1cd0c..84d3195 100644
--- a/private/rules/coursier.bzl
+++ b/private/rules/coursier.bzl
@@ -1737,6 +1737,8 @@
         "COURSIER_OPTS",
         "COURSIER_SHA256",
         "COURSIER_URL",
+        "REPIN",
+        "RULES_JVM_EXTERNAL_REPIN",
         "RJE_VERBOSE",
         "XDG_CACHE_HOME",
     ],