Fix math library not linked with lib/gvc for Linux CMake builds

This is what the autotools builds do.

$(MATH_LIB) was already referenced by lib/gvc/CmakeLists.txt, but it
was never given any value.

For Windows, this is not necessary since math functions are included
in the Universal C Runtime library (UCRT).

Without this, the rtest/test_examples.py gave errors like this for e.g. demo.c:

/usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libgvc.so: undefined reference to `atan2'

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 63a493e24c2f5ba33bb691644f822e70459a7705..e42faae1de87d7fd98c9869178fb37536b3b8135 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -85,6 +85,10 @@ find_package(LTDL)
 find_package(PangoCairo)
 find_package(ZLIB)
 
+if (UNIX)
+    find_library(MATH_LIB m)
+endif ()
+
 if (WIN32)
     # Find Windows specific dependencies
     find_package(RxSpencer REQUIRED)