PPC64LE and S390X support

Start with the Makefile build section and reproduce the AIX ppc64 build using the reported command. Inspect the listed vendor files and their terminal-input paths to identify the AIX failures; done means the PPC64LE, S390X, and AIX targets build successfully, with the requested non-interactive AIX behavior.

@beardedprincess

BUSINESS PROBLEM

Extra platform support for VSSH-CLI. Customer has Linux and AIX on S390x

PROPOSED SOLUTION

We have a solution for Linux on PPC64LE and S390X, we have already tested this and it produced a working binary:
Test on RHEL8 on PPC64LE and S390x:
In Makefile, in the build section, add lines for the additional targets:
env GOOS=linux CGO_ENABLED=0 GOARCH=s390x go build -ldflags '$(GO_LDFLAGS)' -o bin/linux_s390x/vssh ./cmd
env GOOS=linux CGO_ENABLED=0 GOARCH=ppc64le go build -ldflags '$(GO_LDFLAGS)' -o bin/linux_ppc64le/vssh ./cmd

For the AIX port, there's a commented line for AIX already, however the build fails with these errors:
vssh-cli-source> gmake build
! gofmt -l . | grep -v ^vendor/ | grep .
go get ./...
env GOOS=aix CGO_ENABLED=0 GOARCH=ppc64 go build -ldflags '-X "github.com/venafi/vssh-cli/cmd/common.VersionString=1.0.2025041518" -X "github.com/venafi/vssh-cli/cmd/common.VersionBuildTimeStamp=20250415.184158" -s -w' -o bin/aix_ppc64/vssh ./cmd

github.com/inconshreveable/go-update/internal/osext

vendor/github.com/inconshreveable/go-update/internal/osext/osext.go:14:12: undefined: executable

github.com/denisbrodbeck/machineid

vendor/github.com/denisbrodbeck/machineid/id.go:29:13: undefined: machineID

github.com/AlecAivazis/survey/v2/terminal

vendor/github.com/AlecAivazis/survey/v2/terminal/runereader_posix.go:48:43: undefined: syscall.SYS_IOCTL
vendor/github.com/AlecAivazis/survey/v2/terminal/runereader_posix.go:48:81: undefined: ioctlReadTermios
vendor/github.com/AlecAivazis/survey/v2/terminal/runereader_posix.go:60:43: undefined: syscall.SYS_IOCTL
vendor/github.com/AlecAivazis/survey/v2/terminal/runereader_posix.go:60:81: undefined: ioctlWriteTermios
vendor/github.com/AlecAivazis/survey/v2/terminal/runereader_posix.go:68:43: undefined: syscall.SYS_IOCTL
vendor/github.com/AlecAivazis/survey/v2/terminal/runereader_posix.go:68:81: undefined: ioctlWriteTermios

These appear to be in the code for handling terminal input. For our use case, we can provide all necessary input to the tool on the command line, we do not need interactive input. We would be perfectly happy if this code was just bypassed on AIX.

CURRENT ALTERNATIVES

Current alternatives is running vssh commands on supported platforms and then manually transferring the results to unsupported platforms.

To that end, we have build the Linux on PPC64LE and S390x successfully and have those binaries and they work. All we need is AIX. Provided the makefile updates above for your benefit. Go appears to be able to cross-compile just fine.

VENAFI EXPERIENCE

Several years, and we use it daily.