Update build instructions for WASM (#1622)

Emscripten uses static linking, so we should explicitly request a static TBB library instead of

* explicitly asking for shared (current instructions)
* using the default, i.e., shared

Both of the above get overridden with multiple warnings.

WASM_Support.md

@@ -33,7 +33,7 @@ To build the system, run:
 
 ```
 mkdir build && cd build
-emcmake cmake .. -DCMAKE_CXX_COMPILER=em++ -DCMAKE_C_COMPILER=emcc -DTBB_STRICT=OFF -DCMAKE_CXX_FLAGS=-Wno-unused-command-line-argument -DTBB_DISABLE_HWLOC_AUTOMATIC_SEARCH=ON -DBUILD_SHARED_LIBS=ON -DTBB_EXAMPLES=ON -DTBB_TEST=ON
+emcmake cmake .. -DCMAKE_CXX_COMPILER=em++ -DCMAKE_C_COMPILER=emcc -DTBB_STRICT=OFF -DCMAKE_CXX_FLAGS=-Wno-unused-command-line-argument -DTBB_DISABLE_HWLOC_AUTOMATIC_SEARCH=ON -DBUILD_SHARED_LIBS=OFF -DTBB_EXAMPLES=ON -DTBB_TEST=ON
 ```
 To compile oneTBB without ``pthreads``, set the flag ``-DEMSCRIPTEN_WITHOUT_PTHREAD=true`` in the command above. By default, oneTBB uses the ``pthreads``.
 ```