Fix unexpected operator build error on POSIX shells

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

Author: knopers8

Makefile

@@ -127,7 +127,7 @@ $(WHAT): validate-go-version
 	@$(WHAT_$@_BUILD_FLAGS) go build -mod=vendor $(VERBOSE_$(V)) -o bin/$@ $(LDFLAGS) ./cmd/$@
 
 # special case: if the current WHAT is o2-aliecs-executor, also copy over the shmcleaner script
-	@if [ $@ == "o2-aliecs-executor" ]; then \
+	@if [ $@ = "o2-aliecs-executor" ]; then \
 		echo -e "\033[1;33mcopy\033[0m ./o2-aliecs-shmcleaner  \033[1;33m==>\033[0m  \033[1;34m./bin/o2-aliecs-shmcleaner\033[0m"; \
 		cp o2-aliecs-shmcleaner bin/o2-aliecs-shmcleaner; \
 		chmod +x bin/o2-aliecs-shmcleaner; \
@@ -140,7 +140,7 @@ $(INSTALL_WHAT): validate-go-version
 	@$(WHAT_$(@:install_%=%)_BUILD_FLAGS) go install -mod=vendor $(VERBOSE_$(V)) $(LDFLAGS) ./cmd/$(@:install_%=%)
 
 # special case: if the current WHAT is o2-aliecs-executor, also copy over the shmcleaner script
-	@if [ $@ == "install_o2-aliecs-executor" ]; then \
+	@if [ $@ = "install_o2-aliecs-executor" ]; then \
 		echo -e "\033[1;33minstall\033[0m ./o2-aliecs-shmcleaner  \033[1;33m==>\033[0m  \033[1;34m$$GOPATH/bin/o2-aliecs-shmcleaner\033[0m"; \
 		cp o2-aliecs-shmcleaner $${GOPATH}/bin/o2-aliecs-shmcleaner; \
 		chmod +x $${GOPATH}/bin/o2-aliecs-shmcleaner; \