Skip unsupported linker options on illumos.

Building on illumos currently fails with:

```
ld: fatal: unrecognized option '--gc-sections'
```

This happens because `--gc-sections` isn't supported on illumos `ld`.
This patch updates CMakeLists.txt to skip unsupported linker options on
illumos. The flags used on other operating systems are optimizations
that don't affect correctness, so this change is safe.

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8c8a86cb5f2b20b975205eeef0f1b6dd568fe44d..a4c9667e2f4e12090440cb8048534539147d2775 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -139,7 +139,12 @@ IF (CMAKE_C_COMPILER_ID MATCHES "^GNU$" OR
   # either of the following two, yet neither is supported as of 3.0.2
   # - check_linker_flag - does not exist
   # - try_compile - does not support linker flags
-  IF(NOT CMAKE_SYSTEM_NAME MATCHES "Darwin")
+  IF(CMAKE_SYSTEM_NAME MATCHES "Darwin")
+    SET(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,-dead_strip")
+    SET(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-dead_strip")
+  ELSEIF(CMAKE_SYSTEM_NAME MATCHES "SunOS")
+    # SunOS linker doesn't support --gc-sections
+  ELSE()
     # Place the functions and data into separate sections, allowing the linker
     # to garbage collect the unused ones.
     SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -ffunction-sections -fdata-sections")
@@ -148,10 +153,7 @@ IF (CMAKE_C_COMPILER_ID MATCHES "^GNU$" OR
     # Printing the discarded section is "too much", so enable on demand.
     #SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -Wl,--print-gc-sections")
     #SET(CMAKE_SHARED_LINKER_FLAGS_DEBUG "${CMAKE_SHARED_LINKER_FLAGS_DEBUG} -Wl,--print-gc-sections")
-  ELSE()
-    SET(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,-dead_strip")
-    SET(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-dead_strip")
-  ENDIF(NOT CMAKE_SYSTEM_NAME MATCHES "Darwin")
+  ENDIF()
 ENDIF (CMAKE_C_COMPILER_ID MATCHES "^GNU$" OR
        CMAKE_C_COMPILER_ID MATCHES "^Clang$" AND NOT MSVC)
 IF (CMAKE_C_COMPILER_ID MATCHES "^XL$")