Improve wording of Emscripten's design goal

Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com>

Author: juntyr

src/doc/rustc/src/platform-support/wasm32-unknown-emscripten.md

@@ -4,11 +4,12 @@
 
 The `wasm32-unknown-emscripten` target is a WebAssembly compilation target which
 uses the [Emscripten](https://emscripten.org/) compiler toolchain. Emscripten is
-a C/C++ toolchain used for running C/C++ code on the web. It provides POSIX `libc`
-and `libstd` implementations, access to the OpenGL and SDL APIs, and the ability
-to run arbitrary JavaScript code, all based on web APIs using JS glue code. With
-the `wasm32-unknown-emscripten` target, Rust code can interoperate with
-Emscripten's ecosystem, C/C++ and JS code, and web APIs.
+a C/C++ toolchain designed to make it as easy as possible to port C/C++ code
+written for Linux to run on the web. It thus provides POSIX-compatible (musl) `libc`
+and `libstd` implementations and many Linux APIs, access to the OpenGL and SDL APIs,
+and the ability to run arbitrary JavaScript code, all based on web APIs using JS
+glue code. With the `wasm32-unknown-emscripten` target, Rust code can interoperate
+with Emscripten's ecosystem, C/C++ and JS code, and web APIs.
 
 One existing user of this target is the
 [`pyodide` project](https://pyodide.org/) which provides a Python runtime in