Ensure RBE_CXX_POOL and RBE_JAVA_POOL variables work as expected

These environment variables are not being passed onto compile actions created from makefiles. This change makes sure that these env variables are passed along so that we are able to update the C++ / Javac pool being used

Test: Ran a build with RBE_CXX_POOL=cpp_next to test the next pool
Bug: b/199774309
Change-Id: Icd47d3647b962a6c3ac712369466d5502b817fd7
diff --git a/core/rbe.mk b/core/rbe.mk
index 19c0e42..370d4bd 100644
--- a/core/rbe.mk
+++ b/core/rbe.mk
@@ -22,6 +22,18 @@
     rbe_dir := prebuilts/remoteexecution-client/live/
   endif
 
+  ifdef RBE_CXX_POOL
+    cxx_pool := $(RBE_CXX_POOL)
+  else
+    cxx_pool := default
+  endif
+
+  ifdef RBE_JAVA_POOL
+    java_pool := $(RBE_JAVA_POOL)
+  else
+    java_pool := java16
+  endif
+
   ifdef RBE_CXX_EXEC_STRATEGY
     cxx_rbe_exec_strategy := $(RBE_CXX_EXEC_STRATEGY)
   else
@@ -59,8 +71,8 @@
   endif
 
   platform := container-image=docker://gcr.io/androidbuild-re-dockerimage/android-build-remoteexec-image@sha256:582efb38f0c229ea39952fff9e132ccbe183e14869b39888010dacf56b360d62
-  cxx_platform := $(platform),Pool=default
-  java_r8_d8_platform := $(platform),Pool=java16
+  cxx_platform := $(platform),Pool=$(cxx_pool)
+  java_r8_d8_platform := $(platform),Pool=$(java_pool)
 
   RBE_WRAPPER := $(rbe_dir)/rewrapper
   RBE_CXX := --labels=type=compile,lang=cpp,compiler=clang --env_var_allowlist=PWD --exec_strategy=$(cxx_rbe_exec_strategy) --platform=$(cxx_platform) --compare=$(cxx_compare)