Don't test wasmtime-wasi-c on Windows. (#299)

test-all.sh

@@ -53,7 +53,6 @@ banner "Rust unit tests"
 RUST_BACKTRACE=1 cargo test \
   --package wasmtime \
   --package wasmtime-wasi \
-  --package wasmtime-wasi-c \
   --package wasmtime-wast \
   --package wasmtime-debug \
   --package wasmtime-environ \
@@ -62,6 +61,12 @@ RUST_BACKTRACE=1 cargo test \
   --package wasmtime-interface-types \
   --package wasmtime-obj \
 
+# Test wasmtime-wasi-c, which doesn't support Windows.
+if [ "${OS:-Not}" != "Windows_NT" ]; then
+    RUST_BACKTRACE=1 cargo test \
+      --package wasmtime-wasi-c
+fi
+
 # Make sure the documentation builds.
 banner "Rust documentation: $topdir/target/doc/wasmtime/index.html"
 cargo doc