I am fairly new to OSX so please bare with me.

I am trying to compile an older application that requires qt 5.6 on my Catalina 10.15.2 system. I was able to do this on other systems previously that were on OSX 10.11 and 10.14 but I am struggling with 10.15.
The final application targets OSX 10.9 +.

I have :

• downloaded qt-everywhere-opensource-src-5.6.3 package.
• updated the qtbase/mkspecs/macx-clang/qmake.conf with:
  QMAKE_MACOSX_DEPLOYMENT_TARGET = 10.9
• set MINIMUM_SDK_VERSION of XCode 10.11 (Since I know this worked on the other system)

The configuration goes fine but when I build, I am mainly getting a bunch of deeper SDK errors in the like of:

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/System/Library/Frameworks/ApplicationServices.framework/Frameworks/HIServices.framework/Headers/Processes.h:412:34: note: 
      expanded from macro 'MacGetCurrentProcess'
    #define MacGetCurrentProcess GetCurrentProcess
                                 ^
qcocoahelpers.mm:547:6: error: functions that differ only in their return type cannot be overloaded
void qt_mac_drawCGImage(CGContextRef inContext, const CGRect *inBounds, CGImageRef inImage)


/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/System/Library/Frameworks/CoreServices.framework/Frameworks/CarbonCore.framework/Headers/Components.h:593:1: note: 
      'CloseComponent' has been explicitly marked deprecated here
CloseComponent(ComponentInstance aComponentInstance)          __OSX_AVAILABLE_BUT_DEPRECATED(__MAC_10_0, __MAC_10_8, __IPHONE_NA, __IPHONE_NA);
^
qcocoahelpers.mm:689:5: error: call to 'qt_mac_drawCGImage' is ambiguous
    qt_mac_drawCGImage(ctx, &rect, image);
~~~~ ^

I know that this is officially not supported, but 10.14 wasn't either. Is there a way around it or am I missing something? Apple won't let me install any other older versions of the Command Line Tools, so I am running out of idea.

Any help would be appreciated, thanks!