Improve tests/runCoreTests.sh
Improve tests/runCoreTests.sh

Added shebang (custom shell support, e.g., zsh)
Replace |& by 2>&1 (old bash version support)

PerfDotNet/BenchmarkDotNet,ig-sinicyn/BenchmarkDotNet,adamsitnik/BenchmarkDotNet,Teknikaali/BenchmarkDotNet,adamsitnik/BenchmarkDotNet,alinasmirnova/BenchmarkDotNet,Teknikaali/BenchmarkDotNet,PerfDotNet/BenchmarkDotNet,alinasmirnova/BenchmarkDotNet,adamsitnik/BenchmarkDotNet,Ky7m/BenchmarkDotNet,Ky7m/BenchmarkDotNet,Ky7m/BenchmarkDotNet,alinasmirnova/BenchmarkDotNet,ig-sinicyn/BenchmarkDotNet,alinasmirnova/BenchmarkDotNet,ig-sinicyn/BenchmarkDotNet,adamsitnik/BenchmarkDotNet,Ky7m/BenchmarkDotNet,Teknikaali/BenchmarkDotNet,PerfDotNet/BenchmarkDotNet,ig-sinicyn/BenchmarkDotNet