Change Cretonne's license to "Apache-2.0 WITH LLVM-exception".

This adds the "LLVM-exception" to Cretonne's existing Apache-2.0
license.

https://spdx.org/licenses/LLVM-exception.html

cranelift/Cargo.toml

@@ -3,7 +3,7 @@ name = "cretonne-tools"
 authors = ["The Cretonne Project Developers"]
 version = "0.13.0"
 description = "Binaries for testing the Cretonne libraries"
-license = "Apache-2.0"
+license = "Apache-2.0 WITH LLVM-exception"
 documentation = "https://cretonne.readthedocs.io/"
 repository = "https://github.com/cretonne/cretonne"
 publish = false

cranelift/LICENSE

@@ -200,3 +200,20 @@
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
+
+
+--- LLVM Exceptions to the Apache 2.0 License ----
+
+As an exception, if, as a result of your compiling your source code, portions
+of this Software are embedded into an Object form of such source code, you
+may redistribute such embedded portions in such Object form without complying
+with the conditions of Sections 4(a), 4(b) and 4(d) of the License.
+
+In addition, if you combine or link compiled forms of this Software with
+software that is licensed under the GPLv2 ("Combined Software") and if a
+court of competent jurisdiction determines that the patent provision (Section
+3), the indemnity provision (Section 9) or other Section of the License
+conflicts with the conditions of the GPLv2, you may retroactively and
+prospectively choose to deem waived or otherwise exclude such Section(s) of
+the License, but only in their entirety and only with respect to the Combined
+Software.