Force C++ linker

Forcing linker language to C causes linker errors when compiling using NDK.

Change-Id: Iea587d1ab00d10b2c331ccc3e178e16c6a78ce5f

examples/CMakeLists.txt

diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index e102e31..8807cd4 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -51,8 +51,8 @@
 
 add_executable(curve_fitting_c curve_fitting.c)
 target_link_libraries(curve_fitting_c PRIVATE Ceres::ceres)
-# Force CMake to link curve_fitting_c using the C linker.
-set_target_properties(curve_fitting_c PROPERTIES LINKER_LANGUAGE C)
+# Force CMake to link curve_fitting_c using the C++ linker.
+set_target_properties(curve_fitting_c PROPERTIES LINKER_LANGUAGE CXX)
 # As this is a C file #including <math.h> we have to explicitly add the math
 # library (libm). Although some compilers (dependent upon options) will accept
 # the indirect link to libm via Ceres, at least GCC 4.8 on pure Debian won't.