[llvm-jitlink] Fix detectStubKind() for big endian systems (#79970)

This function is used in `jitlink-check` lines in LIT tests. In #78371 I
missed to swap initial instruction bytes for systems that store the
constants as big-endian.

(cherry picked from commit 8a5bdd8)

llvm/tools/llvm-jitlink/llvm-jitlink.cpp

@@ -1294,10 +1294,11 @@ class MemoryMatcher {
 };
 
 static StringRef detectStubKind(const Session::MemoryRegionInfo &Stub) {
-  constexpr uint32_t Armv7MovWTle = 0xe300c000;
-  constexpr uint32_t Armv7BxR12le = 0xe12fff1c;
-  constexpr uint32_t Thumbv7MovWTle = 0x0c00f240;
-  constexpr uint16_t Thumbv7BxR12le = 0x4760;
+  using namespace support::endian;
+  auto Armv7MovWTle = byte_swap<uint32_t, endianness::little>(0xe300c000);
+  auto Armv7BxR12le = byte_swap<uint32_t, endianness::little>(0xe12fff1c);
+  auto Thumbv7MovWTle = byte_swap<uint32_t, endianness::little>(0x0c00f240);
+  auto Thumbv7BxR12le = byte_swap<uint16_t, endianness::little>(0x4760);
 
   MemoryMatcher M(Stub.getContent());
   if (M.matchMask(Thumbv7MovWTle)) {