使用Core Plot构建iPhone应用程序时，为什么会看到以下链接器错误？

ld: warning: ignoring file /Users/taxtmart5/Library/Developer/Xcode/DerivedData/Solagen_Calculator-cwvwcdlnuukfftakggygqoczxyuy/Build/Products/Debug-iphoneos/libCorePlot-CocoaTouch.a, file was built for archive which is not the architecture being linked (armv6)
Undefined symbols for architecture armv6:
  \"_OBJC_CLASS_$_CPPlotRange\", referenced from:
      objc-class-ref in VerticalBarChart.o
  \"_OBJC_CLASS_$_CPXYGraph\", referenced from:
      objc-class-ref in VerticalBarChart.o
  \"_OBJC_CLASS_$_CPLineStyle\", referenced from:
      objc-class-ref in VerticalBarChart.o
  \"_OBJC_CLASS_$_CPTextStyle\", referenced from:
      objc-class-ref in VerticalBarChart.o
  \"_OBJC_CLASS_$_CPAxisLabel\", referenced from:
      objc-class-ref in VerticalBarChart.o
  \"_OBJC_CLASS_$_CPBarPlot\", referenced from:
      objc-class-ref in VerticalBarChart.o
  \"_CPDecimalFromString\", referenced from:
      -[VerticalBarChart renderInLayer:withTheme:] in VerticalBarChart.o
  \"_OBJC_CLASS_$_CPColor\", referenced from:
      objc-class-ref in PlotItem.o
      objc-class-ref in VerticalBarChart.o
  \"_OBJC_CLASS_$_CPMutableTextStyle\", referenced from:
      objc-class-ref in PlotItem.o
  \"_OBJC_CLASS_$_CPFill\", referenced from:
      objc-class-ref in VerticalBarChart.o
  \"_OBJC_CLASS_$_CPGraphHostingView\", referenced from:
      objc-class-ref in PlotItem.o
  \"_CPDecimalFromFloat\", referenced from:
      -[VerticalBarChart renderInLayer:withTheme:] in VerticalBarChart.o
  \"_kCPPlainWhiteTheme\", referenced from:
      -[VerticalBarChart renderInLayer:withTheme:] in VerticalBarChart.o
  \"_OBJC_CLASS_$_CPTheme\", referenced from:
      objc-class-ref in VerticalBarChart.o
ld: symbol(s) not found for architecture armv6
collect2: ld returned 1 exit status