Specify downstream compiler include paths (#2517)

* #include an absolute path didn't work - because paths were taken to always be relative.

* WIP around testing with NVAPI.

* Make -I work for downstream compilers.
Update docs.

* Small improvement around ignoring tests.

1 files changed, 11 insertions, 0 deletions

diff --git a/docs/command-line-slangc.md b/docs/command-line-slangc.md
index 22266a139..2947c8184 100644
--- a/docs/command-line-slangc.md
+++ b/docs/command-line-slangc.md
@@ -151,6 +151,7 @@ For completeness, here are the options that `slangc` currently accepts:
 
 * -Xname to specify arguments to downstream tool `name` (covered in more detail in "Downstream Arguments")
 
+<a id="downstream-arguments"></a>
 ### Downstream Arguments
 
 During a Slang compilation work may be performed by multiple other stages including downstream compilers and linkers. It isn't possible in general or perhaps even desirable to provide Slang command line equivalents of every option available at every stage of compilation. It is useful to be able to set options specific to a particular compilation stage - to alter code generation, linkage and other options.
@@ -234,6 +235,16 @@ Means that the dxc compilation in the render test (assuming dxc is invoked) will
 -Gfa
 ```
 
+Some options are made available via the same mechanism for all downstream compilers. 
+
+* Use `-I` to specify include path for downstream compilers
+
+For example to specify an include path "somePath" to DXC you can use...
+
+```
+-Xdxc -IsomePath
+```
+
 ### Specifying where dlls/shared libraries are loaded from
 
 On windows if you want a dll loaded from a specific path, the path must be specified absolutely. See the [LoadLibrary documentation](https://docs.microsoft.com/en-us/windows/win32/api/libloaderapi/nf-libloaderapi-loadlibrarya) for more details. A relative path will cause Windows to check all locations along it's search procedure.