Provided by tobtoht, see https://codeberg.org/guix/guix/issues/1234#issuecomment-5838284

diff --git a/include/llvm/Support/Signals.h b/include/llvm/Support/Signals.h
index e0a18e72..c66ea8b3 100644
--- a/include/llvm/Support/Signals.h
+++ b/include/llvm/Support/Signals.h
@@ -15,6 +15,7 @@
 #define LLVM_SUPPORT_SIGNALS_H

 #include <string>
+#include <cstdint>

 namespace llvm {
 class StringRef;