cmake: Make musl support more distro agnostic

CMakeLists.txt

@@ -334,18 +334,11 @@ include_directories(BEFORE ${OPENSSL_INCLUDE_DIR})
 # Make everyone find the highwayhash includes
 include_directories(BEFORE ${CMAKE_CURRENT_SOURCE_DIR}/auxil/highwayhash)
 
-# 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 ()
+# Determine if libfts is external to libc, i.e. musl
+find_package(FTS)
+if ( FTS_FOUND )
+    list(APPEND OPTLIBS ${FTS_LIBRARY})
+    include_directories(BEFORE ${FTS_INCLUDE_DIR})
 endif ()
 
 set(zeekdeps ${zeekdeps}