Remove wasm compile time option and enable wasm behind a runtime flag.

test/mjsunit/mjsunit.status

Index: test/mjsunit/mjsunit.status
diff --git a/test/mjsunit/mjsunit.status b/test/mjsunit/mjsunit.status
index f32b242cb83e03ce23f43a7a570d1c3058bfdf80..598726da6b73d3dbf028b324f36ae802a8e060b3 100644
--- a/test/mjsunit/mjsunit.status
+++ b/test/mjsunit/mjsunit.status
@@ -166,9 +166,6 @@
   # issue 4078:
   'allocation-site-info': [PASS, NO_VARIANTS],
 
-  # Native WASM is not yet enabled by default.
-  'wasm/*': [SKIP],
-
   ##############################################################################
   # Too slow in debug mode with --stress-opt mode.
   'compiler/regress-stacktrace-methods': [PASS, ['mode == debug', SKIP]],
@@ -739,6 +736,28 @@
   'regress/regress-1132': [SKIP],
 }],  # 'arch == ppc and simulator_run == True'
 
+
+# TODO(bradnelson): Figure out why this fails for arm.
+['arch == arm', {
+  'wasm/asm-wasm': [SKIP],
+}],
+
+# TODO(bradnelson): Figure out why this crashes under asan.
+['asan == True', {
+  'wasm/asm-wasm': [SKIP],
+}],
+
+# TODO(titzer): Figure out why parameter passing on 32-bit is broken.
+['arch != x64', {
+  'wasm/params': [SKIP],
+}],
+
+# TODO(titzer): Figure out why arm64 is broken for wasm.
+['arch == arm64', {
+  'wasm/*': [SKIP],
+}],
+
+
 ['ignition == True', {
   'asm/*': [SKIP],
   'compiler/*': [SKIP],
@@ -750,6 +769,7 @@
   'harmony/*': [SKIP],
   'regress/debug*': [SKIP],
   'regress/regress-debug*': [SKIP],
+  'wasm/*': [SKIP],
 
   'allocation-folding': [SKIP],
   'api-call-after-bypassed-exception': [SKIP],