Fuzz using precompiled modules on CI (#3788)

In working on #3787 I see now that our coverage of loading precompiled
files specifically is somewhat lacking, so this adds a config option to
the fuzzers where, if enabled, will round-trip all compiled modules
through the filesystem to test out the mmapped-file case.

Cargo.lock

@@ -1135,6 +1135,15 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4443176a9f2c162692bd3d352d745ef9413eec5782a80d8fd6f8a1ac692a07f7"
 
+[[package]]
+name = "fastrand"
+version = "1.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3fcf0cee53519c866c09b5de1f6c56ff9d647101f81c1964fa632e148896cdf"
+dependencies = [
+ "instant",
+]
+
 [[package]]
 name = "ff"
 version = "0.10.1"
@@ -2373,9 +2382,9 @@ dependencies = [
 
 [[package]]
 name = "redox_syscall"
-version = "0.2.8"
+version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "742739e41cd49414de871ea5e549afb7e2a3ac77b589bcbebe8c82fab37147fc"
+checksum = "8383f39639269cde97d255a32bdb68c047337295414940c68bdd30c2e13203ff"
 dependencies = [
  "bitflags",
 ]
@@ -2816,13 +2825,13 @@ checksum = "64ae3b39281e4b14b8123bdbaddd472b7dfe215e444181f2f9d2443c2444f834"
 
 [[package]]
 name = "tempfile"
-version = "3.2.0"
+version = "3.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dac1c663cfc93810f88aed9b8941d48cabf856a1b111c29a40439018d870eb22"
+checksum = "5cdb1ef4eaeeaddc8fbd371e5017057064af0911902ef36b39801f67cc6d79e4"
 dependencies = [
  "cfg-if 1.0.0",
+ "fastrand",
  "libc",
- "rand 0.8.3",
  "redox_syscall",
  "remove_dir_all",
  "winapi",
@@ -3584,6 +3593,7 @@ dependencies = [
  "env_logger 0.8.3",
  "log",
  "rayon",
+ "tempfile",
  "v8",
  "wasm-encoder",
  "wasm-smith",