AlekSi breakpad-qt is three years old, and the front-panel source in it does not support 64 bits in OSX.
The inability to detect your processor type is what makes it complain about the "Unknown Architecture" - are you on the PDP-11? "
You definitely need a newer version of the breakpad, either from their svn, or from my qt fork keychains at: https://github.com/webitup/qt-breakpad
Now, if you intend to support 10.6 (MACOSX_DEPLOYMENT_TARGET = 10.6), you need to fix the source using https://github.com/webitup/qt-breakpad/commit/71a9fdedd827e5939ba66bfcc0cd6c1c9fbbc87b (→ I don't think so 10)
Then:
You apparently managed to compile directly from the source, so good for that.
Now, if you want to create a frame from the crossbar instead and reference it from your qt / lib application, then the Dave Mateer proposal is the way to go (and it deserves credit). The following worked for me:
cd $BREAKPAD_SOURCE_TREE xcodebuild -sdk macosx10.7 -project src/client/mac/Breakpad.xcodeproj -configuration Release -target Breakpad ARCHS=x86_64 ONLY_ACTIVE_ARCH=YES MACOSX_DEPLOYMENT_TARGET=10.6 GCC_VERSION=com.apple.compilers.llvmgcc42
Please note that I create the target blade instead of All (it seems that you only need it - and the test does not work for me with All, although it creates a usable framework).
And note that you don't need Xcode per-se - only command line tools build.
To use this infrastructure in your QT project:
mac { QMAKE_LFLAGS += -F$$BREAKPAD_PATH/client/mac/build/Release/ LIBS += -framework Breakpad }
And you must be installed.
Finally: I also made a few changes to my own forblpad-qt fork source so that it at least compiles (on OSX!) With the updated version of the breakpad, but I still don't know if it works correctly.
I'm just starting with this plug - if you want to share experiences and / or fix some things there, just ask.