libuv: Compile as C 99 on Solaris 5.11

SunPro 5.13 and below do not compile as c99 by default.

Utilities/cmlibuv/CMakeLists.txt

@@ -230,6 +230,13 @@ if(CMAKE_SYSTEM_NAME STREQUAL "SunOS")
       _XOPEN_SOURCE=500
       )
   else()
+    if(NOT CMAKE_C_STANDARD OR CMAKE_C_STANDARD EQUAL 90)
+      set(CMAKE_C_STANDARD 11)
+    endif()
+    if(CMAKE_VERSION VERSION_LESS 3.8.20170505 AND CMAKE_C_COMPILER_ID STREQUAL "SunPro" AND CMAKE_C_COMPILER_VERSION VERSION_LESS 5.14)
+      # The running version of CMake does not know how to add this flag.
+      set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -xc99")
+    endif()
     list(APPEND uv_defines
       _XOPEN_SOURCE=600
       )