patch flann // gcc // cmake@3.11+ (#9214)

See: https://github.com/mariusmuja/flann/issues/369

var/spack/repos/builtin/packages/flann/linux-gcc-cmakev3.11-plus.patch

@@ -0,0 +1,24 @@
+--- a/src/cpp/CMakeLists.txt
++++ b/src/cpp/CMakeLists.txt
+@@ -29,7 +29,7 @@ if (BUILD_CUDA_LIB)
+ endif()
+ 
+ if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_COMPILER_IS_GNUCC)
+-    add_library(flann_cpp SHARED "")
++    add_library(flann_cpp SHARED "empty.cpp")
+     set_target_properties(flann_cpp PROPERTIES LINKER_LANGUAGE CXX)
+     target_link_libraries(flann_cpp -Wl,-whole-archive flann_cpp_s -Wl,-no-whole-archive)
+ 
+@@ -83,7 +83,7 @@ if (BUILD_C_BINDINGS)
+     set_property(TARGET flann_s PROPERTY COMPILE_DEFINITIONS FLANN_STATIC)
+ 
+     if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_COMPILER_IS_GNUCC)
+-        add_library(flann SHARED "")
++        add_library(flann SHARED "empty.cpp")
+         set_target_properties(flann PROPERTIES LINKER_LANGUAGE CXX)
+         target_link_libraries(flann -Wl,-whole-archive flann_s -Wl,-no-whole-archive)
+     else()
+--- /dev/null
++++ b/src/cpp/empty.cpp
+@@ -0,0 +1 @@
++/* empty */

var/spack/repos/builtin/packages/flann/package.py

@@ -95,6 +95,9 @@ def url_for_version(self, version):
     depends_on('hdf5', type='test')
     depends_on('gtest', type='test')
 
+    # See: https://github.com/mariusmuja/flann/issues/369
+    patch('linux-gcc-cmakev3.11-plus.patch', when='%gcc^cmake@3.11:')
+
     def patch(self):
         # Fix up the python setup.py call inside the install(CODE
         filter_file("setup.py install",