Fix typo in docs/DevelopmentTips.md: boostrapping -> bootstrapping

Author: cbjeukendrup

docs/DevelopmentTips.md

@@ -21,17 +21,17 @@ Going further, for various reasons the standard library has lots of warnings. Th
 Copy the invocation that has  ` -o <build-path>/swift-macosx-x86_64/stdlib/public/core/iphonesimulator/i386/Swift.o`, so that we can perform the actual call to swiftc ourselves. Tack on `-suppress-warnings` at the end, and now we have the command to just build `Swift.o` for i386 while only displaying the actual errors.
 
 ### Choosing the bootstrapping mode
-By default, the compiler builds with the `boostrapping-with-hostlibs` (macOS) or `bootstrapping` (Linux) bootstrapping mode. To speed up local development it's recommended to build with the `hosttools` mode: `utils/build-script --bootstrapping=hosttools`.
+By default, the compiler builds with the `bootstrapping-with-hostlibs` (macOS) or `bootstrapping` (Linux) bootstrapping mode. To speed up local development it's recommended to build with the `hosttools` mode: `utils/build-script --bootstrapping=hosttools`.
 
 It requires a recently new swift toolchain to be installed on your build machine. You might need to download and install a nightly Swift toolchain to build the Swift project in `hosttools` mode.
 
 Not that changing the bootstrapping mode needs a reconfiguration.
 
 #### Using a locally built Swift toolchain
 
-If you do not want to install a nightly Swift toolchain, or you need to debug Swift code within SwiftCompilerSources, you can build the Swift toolchain in `boostrapping-with-hostlibs` mode on your local machine once, and then use this toolchain to iterate on your changes with the `hosttools` mode:
+If you do not want to install a nightly Swift toolchain, or you need to debug Swift code within SwiftCompilerSources, you can build the Swift toolchain in `bootstrapping-with-hostlibs` mode on your local machine once, and then use this toolchain to iterate on your changes with the `hosttools` mode:
 
-* Build the toolchain locally in `boostrapping-with-hostlibs` mode: `./utils/build-toolchain com.yourname`.
+* Build the toolchain locally in `bootstrapping-with-hostlibs` mode: `./utils/build-toolchain com.yourname`.
 * Copy the `swift-LOCAL-YYYY-MM-DD.xctoolchain` file from `./swift-nightly-install/Library/Developer/Toolchains` to `/Library/Developer/Toolchains`.
 * Launch Xcode, in the menu bar select _Xcode_ > _Toolchains_ > _Local Swift Development Snapshot YYYY-MM-DD_.
 * Remove the Swift build directory: `./build`.
@@ -124,4 +124,4 @@ To setup this environment a few steps are necessary:
 
 Now you are all set. You can build and debug like with a native Xcode project.
 
-If the project structure changes, e.g. new source files are added or deleted, you just have to re-create the LLVM and Swift projects with `utils/build-script --skip-build --xcode --skip-early-swift-driver`.
+If the project structure changes, e.g. new source files are added or deleted, you just have to re-create the LLVM and Swift projects with `utils/build-script --skip-build --xcode --skip-early-swift-driver`.