Document IREE-specific CMake options
First attempt to solve #2111. There is still room to improve the layout.
Closes https://github.com/google/iree/pull/2230
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/iree/pull/2230 from iml130:docs b607d5e17b0375edb5249480b8197df15bf8c77c
PiperOrigin-RevId: 317200804
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+# IREE-specific CMake Options and Variables
+
+This gives a brief explanation of IREE specific CMake options and variables.
+
+* `IREE_ENABLE_RUNTIME_TRACING`:BOOL
+
+ Enables instrumented runtime tracing. Defaults to `OFF`.
+
+* `IREE_ENABLE_MLIR`:BOOL
+
+ Enables MLIR/LLVM dependencies. Defaults to `ON`.
+
+* `IREE_ENABLE_EMITC`:BOOL
+
+ Enables MLIR EmitC dependencies. Defaults to OFF. Requires that
+ `IREE_ENABLE_MLIR` is set to `ON`.
+
+* `IREE_BUILD_COMPILER`:BOOL
+
+ Builds the IREE compiler. Defaults to `ON`.
+
+* `IREE_BUILD_TESTS`:BOOL
+
+ Builds IREE unit tests. Defaults to `ON`.
+
+* `IREE_BUILD_DOCS`:BOOL
+
+ Builds IREE documentation. Defaults to `OFF`.
+
+* `IREE_BUILD_SAMPLES`:BOOL
+
+ Builds IREE sample projects. Defaults to `ON`.
+
+* `IREE_BUILD_DEBUGGER`:BOOL
+
+ Builds the IREE debugger app. Defaults to `OFF`.
+
+* `IREE_BUILD_PYTHON_BINDINGS`:BOOL
+
+ Builds the IREE python bindings Defaults to `OFF`.
+
+* `IREE_BUILD_EXPERIMENTAL`:BOOL
+
+ Builds experimental projects. Defaults to `OFF`.
+
+* `IREE_HAL_DRIVERS_TO_BUILD`:STRING
+
+ *This does not have any effect at the moment, but will be supported in the
+ future!* Semicolon-separated list of HAL drivers to build, or `all` for
+ building all HAL drivers. Case-insensitive. Defaults to `all`. Example:
+ `-DIREE_HAL_DRIVERS_TO_BUILD="Vulkan;VMLA"`.
+
+* `IREE_TARGET_BACKENDS_TO_BUILD`:STRING
+
+ *This does not have any effect at the moment, but will be supported in the
+ future!* Semicolon-separated list of HAL drivers to build, or `all` for
+ building all HAL drivers. Case-insensitive. Defaults to `all`. Example:
+ `-DIREE_HAL_DRIVERS_TO_BUILD="Vulkan_SPIRV;VMLA"`.
+
+* `IREE_ENABLE_LLD`:BOOL
+
+ Use lld when linking. Defaults to `OFF`.
+
+* `IREE_MLIR_DEP_MODE`:STRING
+
+ Defines the MLIR dependency mode. Case-sensitive. Can be `BUNDLED`,
+ `DISABLED` or `INSTALLED`. Defaults to `BUNDLED`. If set to `INSTALLED`, the
+ variable `MLIR_DIR` needs to be passed and that LLVM needs to be compiled
+ with `LLVM_ENABLE_RTTI` set to `ON`.
+
+* `MLIR_DIR`:STRING
+
+ Specifies the path where to look for the installed MLIR/LLVM packages.
+ Required if `IREE_MLIR_DEP_MODE` is set to `INSTALLED`.
