doc(test-termination/README): specify environment

The new text at the bottom of the test-termination/README.md
specifies the environment variable definitions used in running
the termination tests.

test-termination/README.md

@@ -1,6 +1,6 @@
 Test Termination
 ----------------
-The code in this subdirectory intentionally terminate to test the following
+The code in this subdirectory intentionally terminate to tests the following
 procedures and interface from  prif.F90:
   - `prif_error_stop`
   - `prif_register_stop_callback`
@@ -35,3 +35,19 @@ which should yield trailing output similar to the following:
 <ERROR> *cmd_run*:stopping due to failed executions
 STOP 1
 ```
+The environment variables that might be relevant to reproducing the above behavior
+include `FPM_FC`, `FPM_CC`, `FPM_FFLAGS`, `LC_RPATH`, and either `DYLD_LIBRARY_PATH`
+on macOS or `LD_LIBRARY_PATH` on Linux.  On the macOS system tested, `FPM_FC`
+and `FPM_CC` point to `flang-new` and `clang` (version information below), whereas
+`LC_RPATH` and `DYLD_LIBRARY_PATH` are both set to the same path as that of `flang-new`
+but with the trailing `bin` replaced by `lib`.
+
+```
+% flang-new --version
+flang-new version 20.0.0git ([email protected]:ROCm/llvm-project 27e3c3a2c5716678cef303ba211ccea46a421b00)
+Target: arm64-apple-darwin23.6.0
+Thread model: posix
+InstalledDir: /Users/rouson/Repositories/llvm-project/install/rocm/bin
+Build config: +assertions
+```
+