internal/fuzz: update to use native go-fuzz

Fixes golang/protobuf#1084.

Change-Id: I2c71e9f58d09345d13f461ec78ee4e39c3a7f06d
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/228277
Reviewed-by: Joe Tsai <joetsai@google.com>

internal/fuzz/README.md

@@ -5,9 +5,10 @@ Fuzzing support using [go-fuzz](https://github.com/dvyukov/go-fuzz).
 Basic operation:
 
 ```sh
-$ go install github.com/dvyukov/go-fuzz/go-fuzz github.com/dvyukov/go-fuzz/go-fuzz-build
+$ go install github.com/dvyukov/go-fuzz/go-fuzz
+$ go install github.com/mdempsky/go114-fuzz-build
 $ cd internal/fuzz/{fuzzer}
-$ GOFUZZ111MODULE=on go-fuzz-build .
+$ go114-fuzz-build google.golang.org/protobuf/internal/fuzz/{fuzzer}
 $ go-fuzz
 ```
 

internal/fuzz/oss-fuzz-build.sh

@@ -10,7 +10,7 @@ function compile_fuzzer {
   fuzzer=$3
 
    # Instrument all Go files relevant to this fuzzer
-  go-fuzz-build -tags=protolegacy -libfuzzer -func $function -o $fuzzer.a $path
+  go-fuzz -tags=protolegacy -func $function -o $fuzzer.a $path
 
    # Instrumented, compiled Go ($fuzzer.a) + fuzzing engine = fuzzer binary
   $CXX $CXXFLAGS $LIB_FUZZING_ENGINE $fuzzer.a -lpthread -o $OUT/$fuzzer
@@ -19,7 +19,7 @@ function compile_fuzzer {
 for x in internal/fuzz/*; do
   if [ -d $x/corpus ]; then
     name=$(basename $x)
-    compile_fuzzer ./$x Fuzz $name
+    compile_fuzzer google.golang.org/protobuf/$x Fuzz $name
     zip -jr $OUT/${name}_seed_corpus.zip $x/corpus
   fi
 done