guix: use Clang & LLVM 19 for macOS build

contrib/guix/manifest.scm

@@ -567,9 +567,9 @@ inspecting signatures in Mach-O binaries.")
                  (list gcc-toolchain-13 "static")
                  (make-bitcoin-cross-toolchain target)))
           ((string-contains target "darwin")
-           (list clang-toolchain-18
-                 lld-18
-                 (make-lld-wrapper lld-18 #:lld-as-ld? #t)
+           (list clang-toolchain-19
+                 lld-19
+                 (make-lld-wrapper lld-19 #:lld-as-ld? #t)
                  python-signapple
                  zip))
           (else '())))))

contrib/guix/symbol-check.py

@@ -258,7 +258,7 @@ def check_MACHO_sdk(binary) -> bool:
     return False
 
 def check_MACHO_lld(binary) -> bool:
-    if binary.build_version.tools[0].version == [18, 1, 8]:
+    if binary.build_version.tools[0].version == [19, 1, 4]:
         return True
     return False