llvm18: -include cstdint (gcc/clang 15 no arrastran <cstdint> ⇒ uint64_t undeclared en SmallVector.h)

LLVM 18.1.8 usa uint64_t sin incluir <cstdint>; libstdc++ 15 ya no lo trae transitivo.
Fix estándar upstream vía flag. Pasó de morir en [14/2378] a compilar limpio.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

recipes/llvm18.toml

@@ -27,6 +27,8 @@ CC=gcc CXX='g++ -static-libstdc++ -static-libgcc' \
 cmake -S llvm -B build -G Ninja \
   -DCMAKE_BUILD_TYPE=Release \
   -DCMAKE_INSTALL_PREFIX=/usr \
+  -DCMAKE_CXX_FLAGS="-include cstdint" \
+  -DCMAKE_C_FLAGS="-include stdint.h" \
   -DLLVM_TARGETS_TO_BUILD=X86 \
   -DLLVM_BUILD_LLVM_DYLIB=ON \
   -DLLVM_LINK_LLVM_DYLIB=ON \