Extra explanation on how installer relays CMake args

hpvm/docs/install.rst

@@ -71,11 +71,22 @@ Use HPVM installer script to download, configure and build HPVM along with LLVM
 
    ./install.sh
 
-
 * Without arguments, this script will interactively prompt you for some parameters.
   Alternatively, use ``./install.sh -h`` for a list of available arguments
   and pass arguments as required.
 
+* ``./install.sh`` can relay additional arguments to CMake, but the dash must be dropped
+  regardless of using prompt or CLI arguments.
+  For example, 
+
+  .. code-block:: shell
+
+   ./install.sh -j32 DCMAKE_BUILD_TYPE=Release
+
+  will compile HPVM with 32 threads in Release mode; similarly, inputting
+  ``DCMAKE_BUILD_TYPE=Release`` to the prompt will also send ``-DCMAKE_BUILD_TYPE=Release``
+  to CMake which gives a build in Release mode.
+
 After configuring HPVM,
 the installer will also compile HPVM by default, which you can opt out of.
 If you do so, follow the next section "Manually Build HPVM" to manually compile HPVM,