Add features for building with fuzzing but not linking libfuzzer

Signed-off-by: Victor Porof <victor.porof@gmail.com>

Cargo.toml

@@ -56,3 +56,4 @@ default = []
 with-clang = ["lmdb-rkv-sys/with-clang"]
 with-asan = ["lmdb-rkv-sys/with-asan"]
 with-fuzzer = ["lmdb-rkv-sys/with-fuzzer"]
+with-fuzzer-no-link = ["lmdb-rkv-sys/with-fuzzer-no-link"]

lmdb-sys/Cargo.toml

@@ -36,6 +36,7 @@ default = []
 with-clang = []
 with-asan = ["with-clang"]
 with-fuzzer = ["with-clang"]
+with-fuzzer-no-link = ["with-clang"]
 
 # These features configure the MDB_IDL_LOGN macro, which determines
 # the size of the free and dirty page lists (and thus the amount of memory

lmdb-sys/build.rs

@@ -32,12 +32,23 @@ const MDB_IDL_LOGN: u8 = 15;
 )))]
 const MDB_IDL_LOGN: u8 = 16;
 
+macro_rules! warn {
+    ($message:expr) => {
+        println!("cargo:warning={}", $message);
+    };
+}
+
 fn main() {
     let mut lmdb = PathBuf::from(&env::var("CARGO_MANIFEST_DIR").unwrap());
     lmdb.push("lmdb");
     lmdb.push("libraries");
     lmdb.push("liblmdb");
 
+    if cfg!(feature = "with-fuzzer") && cfg!(feature = "with-fuzzer-no-link") {
+        warn!("Features `with-fuzzer` and `with-fuzzer-no-link` are mutually exclusive.");
+        warn!("Building with `-fsanitize=fuzzer`.");
+    }
+
     if !pkg_config::find_library("liblmdb").is_ok() {
         let mut builder = cc::Build::new();
 
@@ -60,6 +71,8 @@ fn main() {
 
         if env::var("CARGO_FEATURE_WITH_FUZZER").is_ok() {
             builder.flag("-fsanitize=fuzzer");
+        } else if env::var("CARGO_FEATURE_WITH_FUZZER_NO_LINK").is_ok() {
+            builder.flag("-fsanitize=fuzzer-no-link");
         }
 
         builder.compile("liblmdb.a")