Build - fix Erlang include path on Linux for sp_link

Author: samaaron

app/external/sp_link/CMakeLists.txt

@@ -15,6 +15,8 @@ endif(NOT MSVC)
 # If we need to change something based on this running on CI, we can use if(DEFINED ENV{GITHUB_ACTION})
 if(APPLE)
     set(ERLANG_INCLUDE_PATH "/usr/local/lib/erlang/usr/include" CACHE PATH "Path to erlang includes")
+elseif(UNIX)
+    set(ERLANG_INCLUDE_PATH "/usr/lib/erlang/usr/include" CACHE PATH "Path to erlang includes")
 elseif(MSVC)
     if(DEFINED ENV{GITHUB_ACTION})
         set(ERLANG_INCLUDE_PATH "C:/Program Files/erl10.7/usr/include" CACHE PATH "Path to erlang includes")
@@ -70,5 +72,6 @@ elseif(APPLE)
     target_link_libraries(libsp_link Ableton::Link "-framework CoreMIDI -framework CoreAudio -framework CoreFoundation -framework Accelerate -framework QuartzCore -framework AudioToolbox -framework IOKit -framework DiscRecording -framework Cocoa")
 elseif(UNIX)
     add_definitions(-DLINUX=1 -DNDEBUG=1)
+    include_directories(${ERLANG_INCLUDE_PATH})
     target_link_libraries(libsp_link Ableton::Link)
 endif(MSVC)