Add examples

What's Changed

• Add flags/vars2.go by @devlights in #929
• Add main_stdout_ospipe example by @devlights in #930
• Add slices.NormalFullsliceCopy by @devlights in #931
• Add gcflags and ldflags example by @devlights in #932
• Add basic/cmdexec/ospipe.go by @devlights in #933
• Add singleapp/git_backup by @devlights in #934
• Add examples/testing/be_library/equal by @devlights in #935
• Add examples/testing/be_library/err by @devlights in #936
• Add examples/testing/be_library/true by @devlights in #937

Full Changelog: v0.5.38...v0.5.39