[llvm] [llvm-dlltool] Implement the --identify option (PR #127465)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-aarch64-libcxx` running on `linaro-flang-aarch64-libcxx` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/89/builds/17050

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (build-unified-tree) failure: build (failure)
...
53.266 [3356/21/3977] Building CXX object tools/mlir/lib/Conversion/GPUToSPIRV/CMakeFiles/obj.MLIRGPUToSPIRV.dir/GPUToSPIRV.cpp.o
53.269 [3356/20/3978] Building CXX object tools/mlir/lib/Conversion/GPUToSPIRV/CMakeFiles/obj.MLIRGPUToSPIRV.dir/WmmaOpsToSPIRV.cpp.o
53.273 [3356/19/3979] Building CXX object tools/mlir/lib/Conversion/LinalgToStandard/CMakeFiles/obj.MLIRLinalgToStandard.dir/LinalgToStandard.cpp.o
53.274 [3356/18/3980] Linking CXX shared library lib/libMLIRConvertToLLVMInterface.so.21.0git
53.274 [3356/17/3981] Creating library symlink lib/libLLVMObjCopy.so
53.275 [3356/16/3982] Creating library symlink lib/libLLVMObjectYAML.so
53.288 [3352/19/3983] Creating library symlink lib/libLLVMDebugInfoDWARF.so
53.289 [3352/18/3984] Creating library symlink lib/libLLVMJITLink.so
53.289 [3352/17/3985] Creating library symlink lib/libLLVMRuntimeDyld.so
53.290 [3352/16/3986] Linking CXX shared library lib/libLLVMDlltoolDriver.so.21.0git
FAILED: lib/libLLVMDlltoolDriver.so.21.0git 
: && /usr/local/bin/c++ -fPIC -stdlib=libc++ -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -stdlib=libc++ -Wl,-z,defs -Wl,-z,nodelete   -Wl,-rpath-link,/home/tcwg-buildbot/worker/flang-aarch64-libcxx/build/./lib  -Wl,--gc-sections -shared -Wl,-soname,libLLVMDlltoolDriver.so.21.0git -o lib/libLLVMDlltoolDriver.so.21.0git lib/ToolDrivers/llvm-dlltool/CMakeFiles/LLVMDlltoolDriver.dir/DlltoolDriver.cpp.o  -Wl,-rpath,"\$ORIGIN/../lib:/home/tcwg-buildbot/worker/flang-aarch64-libcxx/build/lib:"  lib/libLLVMObject.so.21.0git  lib/libLLVMOption.so.21.0git  lib/libLLVMTargetParser.so.21.0git  lib/libLLVMSupport.so.21.0git  -Wl,-rpath-link,/home/tcwg-buildbot/worker/flang-aarch64-libcxx/build/lib && :
/usr/bin/ld: lib/ToolDrivers/llvm-dlltool/CMakeFiles/LLVMDlltoolDriver.dir/DlltoolDriver.cpp.o: in function `llvm::dlltoolDriverMain(llvm::ArrayRef<char const*>)':
DlltoolDriver.cpp:(.text._ZN4llvm17dlltoolDriverMainENS_8ArrayRefIPKcEE+0x62c): undefined reference to `llvm::identify_magic(llvm::StringRef)'
/usr/bin/ld: DlltoolDriver.cpp:(.text._ZN4llvm17dlltoolDriverMainENS_8ArrayRefIPKcEE+0xd5c): undefined reference to `llvm::identify_magic(llvm::StringRef)'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
53.290 [3352/15/3987] Creating library symlink lib/libLLVMLibDriver.so
53.292 [3352/14/3988] Creating library symlink lib/libLLVMXRay.so
53.296 [3352/13/3989] Creating library symlink lib/libMLIRAnalysis.so
53.299 [3352/12/3990] Creating library symlink lib/libMLIRConvertToLLVMInterface.so
53.314 [3352/11/3991] Building CXX object tools/mlir/lib/Dialect/Arith/Transforms/CMakeFiles/obj.MLIRArithTransforms.dir/BufferDeallocationOpInterfaceImpl.cpp.o
53.340 [3352/10/3992] Building CXX object tools/mlir/lib/Dialect/Linalg/Transforms/CMakeFiles/obj.MLIRLinalgTransforms.dir/ConvertConv2DToImg2Col.cpp.o
53.341 [3352/9/3993] Linking CXX shared library lib/libLLVMDebugInfoPDB.so.21.0git
53.360 [3352/8/3994] Building CXX object tools/mlir/lib/Conversion/GPUCommon/CMakeFiles/obj.MLIRGPUToGPURuntimeTransforms.dir/GPUOpsLowering.cpp.o
53.390 [3352/7/3995] Building CXX object tools/mlir/lib/Conversion/LLVMCommon/CMakeFiles/obj.MLIRLLVMCommonConversion.dir/ConversionTarget.cpp.o
53.394 [3352/6/3996] Building CXX object tools/mlir/lib/Dialect/ArmSVE/Transforms/CMakeFiles/obj.MLIRArmSVETransforms.dir/LegalizeVectorStorage.cpp.o
53.398 [3352/5/3997] Building CXX object tools/mlir/lib/Dialect/SPIRV/IR/CMakeFiles/obj.MLIRSPIRVDialect.dir/CastOps.cpp.o
53.400 [3352/4/3998] Building CXX object tools/mlir/lib/Conversion/LLVMCommon/CMakeFiles/obj.MLIRLLVMCommonConversion.dir/MemRefBuilder.cpp.o
53.403 [3352/3/3999] Building CXX object tools/mlir/lib/Conversion/LLVMCommon/CMakeFiles/obj.MLIRLLVMCommonConversion.dir/Pattern.cpp.o
53.405 [3352/2/4000] Building CXX object tools/mlir/lib/Conversion/LLVMCommon/CMakeFiles/obj.MLIRLLVMCommonConversion.dir/LoweringOptions.cpp.o
55.007 [3352/1/4001] Building CXX object lib/LTO/CMakeFiles/LLVMLTO.dir/LTO.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/127465