Feature/premake build (#951)

* * Remove Makefile
* Document how to create build using premake5
* Added support for finding the executable path
* If binDir not set on command line use the executable path

* Fix getting exe path on linux.

* Removed CalcExecutablePath from Path:: interface, made implementation internal.

* Documentation improvements.

* Fixes based on review

* Fix some typos
* Removed unused/needed global

1 files changed, 72 insertions, 4 deletions

diff --git a/docs/building.md b/docs/building.md
index 68e57ec2d..32e4a1156 100644
--- a/docs/building.md
+++ b/docs/building.md
@@ -6,13 +6,81 @@ Clone [this](https://github.com/shader-slang/slang) repository, and then run:
 
     git submodule update --init
 
-The submodule update step is required to pull in the copy of the `glslang` compiler that we currently use for generating SPIR-V.
+The submodule update step is required to pull in dependencies used for testing infrastructure as well as the `glslang` compiler that we currently use for generating SPIR-V. 
 
-## Using Visual Studio
+## Windows Using Visual Studio
 
 Building from source is really only well supported for Windows users with Visual Studio 2015 or later.
-If you are on Windows, then open `slang.sln` and build your desired platform/configuration.
+If you are on Windows, then open `slang.sln` and build your desired platform/configuration. 
 
+The Visual Studio solution in the project is actually just generated using [`premake5`](https://premake.github.io/). See instructions in premake section below for further explanation.
+ 
 ## Linux
 
-For Linux, we include a simple `Makefile`, but it is not designed to be used for active development (e.g., dependency tracking is not handled).
+For building on Linux it is first necessary to generate the `Makefile` for the project - we use [`premake5`](https://premake.github.io/) as the tool used for generating projects from the premake5.lua script found in the root of the project. The section below describes how to use premake on Linux. 
+
+## Premake
+
+Slang uses the tool [`premake5`](https://premake.github.io/) in order to generate projects that can be built on different targets. On Linux premake will generate Makefile/s and on windows it will generate a Visual Studio solution. Information on invoking premake for different kinds of targets can be found [here](https://github.com/premake/premake-core/wiki/Using-Premake). You can also run with `--help` to see available command line options
+
+```
+% premake5 --help
+```
+
+### Windows
+
+First download and install [`premake5`](https://premake.github.io/) on your build system. Open up a command line and go to the root directory of the slang source tree (ie the directory containing `slang.h`).
+ 
+Assuming premake5 is in your `PATH`, you can create a Visual Studio 2015 project for Slang with the following command line
+
+```
+% premake5 vs2015
+```
+
+For Visual Studio 2017 use
+
+```
+% premake5 vs2017
+```
+
+These should create a slang.sln in the same directory and which you can then open in the appropriate Visual Studio. Building will build all of slang and it's test infrastructure.
+
+### Linux 
+
+First download and install [`premake5`](https://premake.github.io/) on your build system. In the terminal go to the root directory of the slang source tree (ie the directory containing `slang.h`). Assuming premake5 is in your `PATH` use  
+
+```
+% premake5 gmake 
+```
+ 
+You can vary the compiler to use via the --cc option with 'gcc' or 'clang' for example
+
+```
+% premake5 gmake --cc=clang
+```
+
+To actually build using make use one of the following
+
+```
+% make config=release_x64
+% make config=debug_x64
+% make config=release_x86
+% make config=debug_x86
+% make config=release_aarch64
+% make config=debug_aarch64
+```
+
+## Testing
+
+When slang is built from source it also builds tools to be able to test the Slang compiler. Testing is achieved using the `slang-test` tool. The binaries are placed in the appropriate directory underneath `bin`. To run the tests on a release x64 build from the command line, in the root directory of slang source tree you can use...
+
+```
+% bin\windows-x64\release\slang-test
+```
+
+Note that on windows if you want to run all of the tests from inside visual studio, it is necessary to set the `Working Directory` under "slang-test project" > "Configuration Properties" > "Debugging" > "Working Directory" to the root directory of the slang source tree. You can do this by setting it to `$(ProjectDir)/../..` for all configurations.
+
+If you only see 'unit-tests' being run (unit tests are prefixed with 'unit-tests/') then the working directory is not correctly set. Most tests are text files describing the test held in the `tests` directory in the root of the slang project. 
+
+See the [documentation on testing](../tools/slang-test/README.md) for more information.
+