[CMake] Add CIR to mlir-headers dependencies (#1927)

This allows generation of the CIR tablegen targets without going through
```
$(ninja -C build_pilot -t targets all | grep IncGen | sed 's/:.*//')
```

Author: badumbatish

clang/include/clang/CIR/Dialect/CMakeLists.txt

@@ -24,5 +24,5 @@ mlir_tablegen(Passes.h.inc -gen-pass-decls -name CIR)
 mlir_tablegen(Passes.capi.h.inc -gen-pass-capi-header --prefix CIR)
 mlir_tablegen(Passes.capi.cpp.inc -gen-pass-capi-impl --prefix CIR)
 add_public_tablegen_target(MLIRCIRPassIncGen)
-
+add_dependencies(mlir-headers MLIRCIRPassIncGen)
 add_clang_mlir_doc(Passes CIRPasses ./ -gen-pass-doc)

clang/include/clang/CIR/Dialect/IR/CMakeLists.txt

@@ -27,6 +27,7 @@ mlir_tablegen(CIROpsStructs.cpp.inc -gen-attrdef-defs)
 mlir_tablegen(CIROpsAttributes.h.inc -gen-attrdef-decls)
 mlir_tablegen(CIROpsAttributes.cpp.inc -gen-attrdef-defs)
 add_public_tablegen_target(MLIRCIREnumsGen)
+add_dependencies(mlir-headers MLIRCIREnumsGen)
 
 clang_tablegen(CIRBuiltinsLowering.inc -gen-cir-builtins-lowering
                SOURCE CIROps.td