Update testcases for upstream Makefile.rules change that removed TRIPLE

The variable was removed in https://reviews.llvm.org/D85539

(cherry picked from commit 70d5319)

Author: adrian-prantl

lldb/test/API/lang/swift/availability/Makefile

@@ -1,3 +1,4 @@
 SWIFT_SOURCES := main.swift
+SWIFTFLAGS_EXTRAS := -target $(TRIPLE)
 
 include Makefile.rules

lldb/test/API/lang/swift/xcode_sdk/Makefile

@@ -1,11 +1,16 @@
 SWIFT_SOURCES := main.swift
+ifeq "$(TRIPLE)" ""
 SWIFTFLAGS_EXTRAS := -Xfrontend -no-serialize-debugging-options
+else
+# Target override for the simulator testcase.
+SWIFTFLAGS_EXTRAS := -Xfrontend -no-serialize-debugging-options -target $(TRIPLE)
+endif
 SWIFT_BRIDGING_HEADER := bridging-header.h
 LD_EXTRAS := ignored.o
 
 all: ignored.o $(EXE)
 
-# Artificially inject a wrong SDK into a C file to test that it is ebing ignored.
+# Artificially inject a wrong SDK into a C file to test that it is being ignored.
 ignored.o: ignored.c
 	$(CC) -target $(ARCH)-apple-macos  -c $< -o $@ \
 	  -isysroot $(shell xcrun --sdk iphonesimulator --show-sdk-path)