Fix unexpected operator build error on POSIX shells

[knopers8]

'==' comparison operator is only supported by Bash, while '=' is supported by both Bash and standard POSIX shells.

[knopers8]

for the reference, this is what the error looks like:

$ make
-e go build -mod=vendor ./cmd/o2-aliecs-core  ==>  ./bin/o2-aliecs-core
/bin/sh: 1: [: o2-aliecs-core: unexpected operator
-e go build -mod=vendor ./cmd/o2-aliecs-executor  ==>  ./bin/o2-aliecs-executor
/bin/sh: 1: [: o2-aliecs-executor: unexpected operator
-e go build -mod=vendor ./cmd/coconut  ==>  ./bin/coconut
/bin/sh: 1: [: coconut: unexpected operator
-e go build -mod=vendor ./cmd/peanut  ==>  ./bin/peanut
/bin/sh: 1: [: peanut: unexpected operator
-e go build -mod=vendor ./cmd/o2-apricot  ==>  ./bin/o2-apricot
/bin/sh: 1: [: o2-apricot: unexpected operator

the build succeeds anyway, but the errors are confusing.