THRIFT-5855: Add swift fuzzers

Add fuzzers for Swift support, to improve the reliability/robustness of the implementation
diff --git a/lib/swift/Makefile.am b/lib/swift/Makefile.am
index ac61716..c681186 100644
--- a/lib/swift/Makefile.am
+++ b/lib/swift/Makefile.am
@@ -28,6 +28,8 @@
 clean-local:
 	swift package clean
 	rm -rf .build
+	rm -rf FuzzTesting/.build
+	rm -rf FuzzTesting/Sources/Fuzz/*
 
 precross:
 	swift build
@@ -35,6 +37,18 @@
 check-local:
 	swift test
 
+FuzzTesting/Sources/Fuzz:
+	mkdir -p FuzzTesting/Sources/Fuzz
+
+fuzz-gen: FuzzTesting/Sources/Fuzz
+	$(top_builddir)/compiler/cpp/thrift --gen swift -r -out FuzzTesting/Sources/Fuzz $(top_srcdir)/test/FuzzTest.thrift
+
+fuzz-local: fuzz-gen
+	cd FuzzTesting && swift build --configuration release ${SWIFTFLAGS}
+
+fuzz: all-local fuzz-local
+	@echo "Built fuzzers successfully"
+
 distdir:
 	$(MAKE) $(AM_MAKEFLAGS) distdir-am
 
@@ -42,6 +56,7 @@
 	Package.swift \
 	Sources \
 	Tests \
+	FuzzTesting \
 	README.md
 
 MAINTAINERCLEANFILES = \