libstrawberry-common: check for library/includes for backtrace() (#364)

This is a non-standard header, so it should be checked properly.
This fixes compilation with musl libc and possibly other C library
implementations.

ext/libstrawberry-common/CMakeLists.txt

@@ -1,8 +1,14 @@
+if (Backtrace_FOUND)
+  include_directories(${Backtrace_INCLUDE_DIRS})
+endif (Backtrace_FOUND)
+
 include_directories(${PROTOBUF_INCLUDE_DIRS})
 include_directories(${CMAKE_CURRENT_BINARY_DIR})
 include_directories(${CMAKE_CURRENT_SOURCE_DIR})
 include_directories(${CMAKE_SOURCE_DIR}/src)
 
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/backtrace_inc.h.in ${CMAKE_CURRENT_BINARY_DIR}/backtrace_inc.h)
+
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall")
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --std=c++11 -U__STRICT_ANSI__ -Wall -Wextra -Wpedantic -Woverloaded-virtual -fpermissive")
@@ -38,6 +44,10 @@ add_library(libstrawberry-common STATIC
   ${MOC}
 )
 
+if (Backtrace_FOUND)
+  target_link_libraries(libstrawberry-common ${Backtrace_LIBRARIES})
+endif (Backtrace_FOUND)
+
 target_link_libraries(libstrawberry-common
   #${PROTOBUF_LIBRARY}
   ${TAGLIB_LIBRARIES}