Revert "Add fuzzer targets for usrsctp."

This reverts commit 36efcfc8.

Reason for revert: Need to revert this in order to revert the last
usrsctp update: https://chromium-review.googlesource.com/c/chromium/src/+/2586379

Original change's description:
> Add fuzzer targets for usrsctp.
>
> Bug: chromium:1025302
> Change-Id: Iadbcb87f0f3f3a1845e925aed8f52685d78e740e
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2108066
> Reviewed-by: Harald Alvestrand <hta@chromium.org>
> Reviewed-by: Florent Castelli <orphis@chromium.org>
> Commit-Queue: Taylor <deadbeef@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#816872}

TBR=hta@chromium.org,deadbeef@chromium.org,orphis@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:1025302
Change-Id: Ib984dc975c5802ad52d07b96d91e8fb1367bc4ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586282Reviewed-by: Harald Alvestrand <hta@chromium.org>
Commit-Queue: Taylor <deadbeef@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836877}

third_party/usrsctp/BUILD.gn

@@ -3,9 +3,8 @@
 # found in the LICENSE file.
 
 import("//build/toolchain/toolchain.gni")
-import("//testing/libfuzzer/fuzzer_test.gni")
 
-config("usrsctp_public_config") {
+config("usrsctp_config") {
   include_dirs = [
     "usrsctplib/usrsctplib",
     "usrsctplib/usrsctplib/netinet",
@@ -18,16 +17,6 @@ config("usrsctp_public_config") {
   }
 }
 
-# Used by both usrsctp static library and fuzzers.
-config("usrsctp_internal_config") {
-  defines = []
-  if (is_linux || is_chromeos || is_android) {
-    defines += [ "_GNU_SOURCE" ]
-  } else if (is_apple) {
-    defines += [ "__APPLE_USE_RFC_2292" ]
-  }
-}
-
 config("usrsctp_warnings") {
   if (is_clang) {
     cflags = [
@@ -129,10 +118,9 @@ static_library("usrsctp") {
     # correctly.
     "//build/config/compiler:no_incompatible_pointer_warnings",
     ":usrsctp_warnings",
-    ":usrsctp_internal_config",
   ]
 
-  public_configs = [ ":usrsctp_public_config" ]
+  public_configs = [ ":usrsctp_config" ]
 
   cflags = [
     "-UINET",
@@ -140,10 +128,14 @@ static_library("usrsctp") {
   ]
 
   if (is_linux || is_chromeos || is_android) {
-    defines += [ "__Userspace_os_Linux" ]
+    defines += [
+      "__Userspace_os_Linux",
+      "_GNU_SOURCE",
+    ]
   } else if (is_apple) {
     defines += [
       "HAVE_SA_LEN",
+      "__APPLE_USE_RFC_2292",
       "__Userspace_os_Darwin",
     ]
   }
@@ -157,51 +149,5 @@ static_library("usrsctp") {
   if (is_fuchsia) {
     defines += [ "__Userspace_os_Fuchsia" ]
   }
-
-  if (use_fuzzing_engine) {
-    defines += [ "INVARIANTS" ]
-  }
   deps = [ "//third_party/boringssl" ]
 }
-
-fuzzer_test("usrsctp_fuzzer_listen") {
-  sources = [
-    "usrsctplib/fuzzer/fuzzer_listen.c",
-    "usrsctplib/programs/programs_helper.c",
-  ]
-  additional_configs = [ ":usrsctp_internal_config" ]
-  deps = [ ":usrsctp" ]
-  seed_corpus = "usrsctplib/fuzzer/CORPUS_LISTEN"
-  libfuzzer_options = [ "max_len=4086" ]
-}
-
-fuzzer_test("usrsctp_fuzzer_fragment") {
-  sources = [
-    "usrsctplib/fuzzer/fuzzer_fragment.c",
-    "usrsctplib/programs/programs_helper.c",
-  ]
-  additional_configs = [ ":usrsctp_internal_config" ]
-  deps = [ ":usrsctp" ]
-  seed_corpus = "usrsctplib/fuzzer/CORPUS_FRAGMENT"
-  libfuzzer_options = [ "max_len=4086" ]
-}
-
-fuzzer_test("usrsctp_fuzzer_connect_multi") {
-  sources = [
-    "usrsctplib/fuzzer/fuzzer_connect.c",
-    "usrsctplib/programs/programs_helper.c",
-  ]
-
-  additional_configs = [ ":usrsctp_internal_config" ]
-
-  # See usrsctplib/fuzzer/CMakeLists.txt.
-  # Stage 0 is "multi", which can start fuzzing at different points during the
-  # handshake based on the first fuzzed byte. There were plans to have dedicated
-  # fuzzers for various stages, but this idea was abandoned what was found that
-  # the "multi" fuzzer performed just as well.
-  defines = [ "FUZZING_STAGE=0" ]
-
-  deps = [ ":usrsctp" ]
-  seed_corpus = "usrsctplib/fuzzer/CORPUS_CONNECT"
-  libfuzzer_options = [ "max_len=32000" ]
-}