Add HIPCC_VERBOSE documentation

Author: harkgill-amd

amd/hipcc/docs/env.rst

@@ -20,3 +20,15 @@ Additional environment variable controls:
 * ``CUDA_PATH``       : Path to the CUDA SDK. The default is ``/usr/local/cuda``. This is only used for NVIDIA platforms.
 * ``HIPCC_COMPILE_FLAGS_APPEND``       : Append extra flags as compilation options to ``hipcc``.
 * ``HIPCC_LINK_FLAGS_APPEND``       : Append extra flags as linking options to ``hipcc``.
+* ``HIPCC_VERBOSE``  : Outputs detailed information on subcommands executed during compilation.
+
+  - ``HIPCC_VERBOSE = 1``: Displays the command to ``clang++`` or ``nvcc`` with all options (`hipcc-cmd`).
+  - ``HIPCC_VERBOSE = 2``: Displays all relevant environment variables and their values.
+  - ``HIPCC_VERBOSE = 4``: Displays only the arguments passed to the ``hipcc`` command (`hipcc_args`).
+  - ``HIPCC_VERBOSE = 5``: Displays both the command to ``clang++`` or ``nvcc`` and ``hipcc`` arguments (`hipcc-cmd` and `hipcc-args`).
+  - ``HIPCC_VERBOSE = 6``: Displays all relevant environment variables and their values, along with the arguments to the ``hipcc`` command.
+  - ``HIPCC_VERBOSE = 7``: Displays all of the above: `hipcc-cmd`, `hipcc-args`, and environment variables.
+ 
+                            
+
+