Enable qa_ngspice to run from build dir on macOS

eeschema/CMakeLists.txt

@@ -20,10 +20,12 @@ set( INC_AFTER ${INC_AFTER} ${NGSPICE_INCLUDE_DIR} )
 # Find out the exact libngspice file name
 get_filename_component( NGSPICE_DLL_ABSPATH "${NGSPICE_DLL}" ABSOLUTE )
 get_filename_component( NGSPICE_DLL_FILE "${NGSPICE_DLL_ABSPATH}" NAME )
+get_filename_component( NGSPICE_DLL_DIR "${NGSPICE_DLL_ABSPATH}" DIRECTORY )
 
 set_property( SOURCE sim/ngspice.cpp
     APPEND PROPERTY COMPILE_DEFINITIONS
     NGSPICE_DLL_FILE="${NGSPICE_DLL_FILE}"
+    NGSPICE_DLL_DIR="${NGSPICE_DLL_DIR}"
     )
 
 include_directories( BEFORE ${INC_BEFORE} )

eeschema/sim/ngspice.cpp

@@ -436,12 +436,12 @@ void NGSPICE::init_dll()
     wxFileName dllFile( "", NGSPICE_DLL_FILE );
 #if defined(__WINDOWS__)
   #if defined( _MSC_VER )
-    const std::vector<std::string> dllPaths = { "" };
+    std::vector<std::string> dllPaths = { "" };
   #else
-    const std::vector<std::string> dllPaths = { "", "/mingw64/bin", "/mingw32/bin" };
+    std::vector<std::string> dllPaths = { "", "/mingw64/bin", "/mingw32/bin" };
   #endif
 #elif defined(__WXMAC__)
-    const std::vector<std::string> dllPaths = {
+    std::vector<std::string> dllPaths = {
         PATHS::GetOSXKicadUserDataDir().ToStdString() + "/PlugIns/ngspice",
         PATHS::GetOSXKicadMachineDataDir().ToStdString() + "/PlugIns/ngspice",
 
@@ -453,9 +453,12 @@ void NGSPICE::init_dll()
                 "/../../../../../Contents/PlugIns/sim"
     };
 #else   // Unix systems
-    const std::vector<std::string> dllPaths = { "/usr/local/lib" };
+    std::vector<std::string> dllPaths = { "/usr/local/lib" };
 #endif
 
+    if( wxGetEnv( wxT( "KICAD_RUN_FROM_BUILD_DIR" ), nullptr ) )
+        dllPaths.emplace_back( NGSPICE_DLL_DIR );
+
 #if defined(__WINDOWS__) || (__WXMAC__)
     for( const auto& path : dllPaths )
     {