[NFC] Canonicalize the "platform" in CI (#11413)

diff --git a/build_tools/cmake/build_android.sh b/build_tools/cmake/build_android.sh
index ad74170..548002f 100755
--- a/build_tools/cmake/build_android.sh
+++ b/build_tools/cmake/build_android.sh
@@ -9,13 +9,13 @@
 # Cross-compile the runtime using CMake targeting Android
 #
 # The required IREE_HOST_BINARY_ROOT environment variable indicates the location
-# of the precompiled IREE binaries. Also requires that ANDROID_ABI and
+# of the precompiled IREE binaries. Also requires that IREE_TARGET_ABI and
 # ANDROID_NDK variables be set. The BUILD_PRESET environment variable indicates
 # how the project should be configured: "test", "benchmark",
 # "benchmark-with-tracing", or "benchmark-suite-test". Defaults to "test".
 #
 # The desired build directory can be passed as the first argument. Otherwise, it
-# uses the environment variable IREE_ANDROID_BUILD_DIR, defaulting to
+# uses the environment variable IREE_TARGET_BUILD_DIR, defaulting to
 # "build-android". Designed for CI, but can be run manually. It reuses the build
 # directory if it already exists. Expects to be run from the root of the IREE
 # repository.
@@ -23,7 +23,8 @@
 
 set -xeuo pipefail
 
-BUILD_DIR="${1:-${IREE_BUILD_ANDROID_DIR:-build-android}}"
+BUILD_DIR="${1:-${IREE_TARGET_BUILD_DIR:-build-android}}"
+ANDROID_ABI="${IREE_TARGET_ABI}"
 IREE_HOST_BINARY_ROOT="$(realpath ${IREE_HOST_BINARY_ROOT})"
 E2E_TEST_ARTIFACTS_DIR="${E2E_TEST_ARTIFACTS_DIR:-build-e2e-test-artifacts/e2e_test_artifacts}"
 BUILD_PRESET="${BUILD_PRESET:-test}"