improvements to cpu targets

[KristofferC]

Use the better multiversion target when creating apps since those might run on other hardware than the machine that built the app. Also use the better "native" for local sysimages.

[KristofferC]

Got

<unknown>:0: error: Cannot represent a difference across sections
Aliasee should be either GlobalValue or ConstantExpr
i32 ()* @julia_main
LLVM ERROR: Broken module found, compilation aborted!

locally, let's see what CI says

[codecov-io]

Codecov Report

Merging #43 into master will decrease coverage by 0.15%.
The diff coverage is 94.44%.

@@            Coverage Diff             @@
##           master      #43      +/-   ##
==========================================
- Coverage   90.69%   90.54%   -0.16%     
==========================================
  Files           2        2              
  Lines         215      222       +7     
==========================================
+ Hits          195      201       +6     
- Misses         20       21       +1

Impacted Files	Coverage Δ
src/PackageCompilerX.jl	90.4% <94.44%> (-0.18%)	⬇️

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