Add cmake compatibility to c-api (#4369)

* Add cmake compatibility to c-api

* Add CMake documentation to wasmtime.h

* Add CMake instructions in examples

* Modify CI for CMake support

* Use correct rust in CI

* Trigger build

* Refactor run-examples

* Reintroduce example_to_run in run-examples

* Replace run-examples crate with cmake

* Fix markdown formatting in examples readme

* Fix cmake test quotes

* Build rust wasm before cmake tests

* Pass CTEST_OUTPUT_ON_FAILURE

* Another cmake test

* Handle os differences in cmake test

* Fix bugs in memory and multimemory examples

examples/threads.c

@@ -1,3 +1,27 @@
+/*
+Example of instantiating of the WebAssembly module and invoking its exported
+function in a separate thread.
+
+You can compile and run this example on Linux with:
+
+   cargo build --release -p wasmtime-c-api
+   cc examples/threads.c \
+       -I crates/c-api/include \
+       -I crates/c-api/wasm-c-api/include \
+       target/release/libwasmtime.a \
+       -lpthread -ldl -lm \
+       -o threads
+   ./threads
+
+Note that on Windows and macOS the command will be similar, but you'll need
+to tweak the `-lpthread` and such annotations as well as the name of the
+`libwasmtime.a` file on Windows.
+
+You can also build using cmake:
+
+mkdir build && cd build && cmake .. && cmake --build . --target wasmtime-threads
+*/
+
 #ifndef _WIN32
 
 #include <inttypes.h>