Update README.md

dependencies/README.md

@@ -1,20 +1,21 @@
 # Dependencies
 
-# LLVM / WASM
+## LLVM / WASM
 
-These are our build wrappers for LLVM and WASM code.
+These are Halide's wrappers for the LLVM and WASM CMake builds/packages.
 
-# SPIR-V
+## SPIR-V
 
 This folder contains a copy of the officially released v1.6 ANSI-C header
 file for [SPIR-V], obtained from the `sdk-1.3.231` branch
 of https://github.com/KhronosGroup/SPIRV-Headers.
 
 The directory structure within this folder matches that of the official
-version's install tree, plus the upstream LICENSE notice.
+version's install tree, plus the upstream `LICENSE` notice, minus files
+that Halide doesn't need.
 
 The `update-spirv.sh` script will automatically acquire the upstream repo,
-build it, and extract the necessary headers and CMake configuration files.
-It takes a single argument, the name of the branch to clone.
+build it, and extract the necessary files. It takes a single argument, the
+name of the branch to clone.
 
-[SPIR-V]: https://www.khronos.org/registry/spir-v/
+[SPIR-V]: https://www.khronos.org/registry/spir-v