Merge remote-tracking branch 'origin/topic/jsiwek/alpine-support'

* origin/topic/jsiwek/alpine-support:
  Add FTS dependency when building on Alpine
  Remove unnecessary header include
  Improve default DNS resolution support for Alpine/musl
  Add dns_resolver option

CMakeLists.txt

@@ -188,6 +188,20 @@ endif ()
 # if one specifies --with-openssl (which may be common).
 include_directories(BEFORE ${OPENSSL_INCLUDE_DIR})
 
+# Alpine support
+if ( ${CMAKE_SYSTEM_NAME} MATCHES Linux AND EXISTS /etc/os-release )
+    execute_process(
+        COMMAND grep -q alpine /etc/os-release
+        RESULT_VARIABLE os_release_alpine
+    )
+
+    if ( os_release_alpine EQUAL 0 )
+        find_package(FTS REQUIRED)
+        list(APPEND OPTLIBS ${FTS_LIBRARY})
+        include_directories(BEFORE ${FTS_INCLUDE_DIR})
+    endif ()
+endif ()
+
 set(brodeps
     ${BinPAC_LIBRARY}
     ${PCAP_LIBRARY}