Add libunwind license

We package libunwind so we also need to distribute its license.

Author: miyuki

CMakeLists.txt

@@ -877,6 +877,7 @@ set(third_party_license_files
     ${llvmproject_SOURCE_DIR}/compiler-rt/LICENSE.TXT   COMPILER-RT-LICENSE.txt
     ${llvmproject_SOURCE_DIR}/libcxx/LICENSE.TXT        LIBCXX-LICENSE.txt
     ${llvmproject_SOURCE_DIR}/libcxxabi/LICENSE.TXT     LIBCXXABI-LICENSE.txt
+    ${llvmproject_SOURCE_DIR}/libunwind/LICENSE.TXT     LIBUNWIND-LICENSE.txt
     ${picolibc_SOURCE_DIR}/COPYING.NEWLIB               COPYING.NEWLIB
     ${picolibc_SOURCE_DIR}/COPYING.picolibc             COPYING.picolibc
 )

cmake/THIRD-PARTY-LICENSES.txt.in

@@ -6,6 +6,7 @@ additional or alternate licenses:
  - compiler-rt: third-party-licenses/COMPILER-RT-LICENSE.txt
  - libc++: third-party-licenses/LIBCXX-LICENSE.txt
  - libc++abi: third-party-licenses/LIBCXXABI-LICENSE.txt
+ - libunwind: third-party-licenses/LIBUNWIND-LICENSE.txt
  - Picolibc: third-party-licenses/COPYING.NEWLIB, third-party-licenses/COPYING.picolibc${mingw_runtime_dlls}
 
 Picolibc licenses refer to its source files. Sources are identified in VERSION.txt.