as/Makefile: Allow conditional features

Supplying a FEATURES argument to the attestation service's Makefile can
conditionally compile features into the build. The FEATURES argument
will disable default features and instead supply the selected features.

For example `FEATURES=restful-bin,rvps-grpc,snp-verifier make grpc-as`
will expand to:

cargo build --bin grpc-as --release \
                        --no-default-features \
                        --features grpc-bin,restful-bin,rvps-grpc,snp-verifier

Signed-off-by: Tyler Fanelli <[email protected]>

attestation-service/Makefile

@@ -8,6 +8,16 @@ BIN_NAMES := grpc-as restful-as
 DEBUG ?=
 DESTDIR ?= $(PREFIX)/bin
 
+FEATURES ?=
+
+ifdef FEATURES
+	OPTIONAL_FEATURES := ,$(FEATURES)
+	default-features := --no-default-features
+else
+	OPTIONAL_FEATURES :=
+	default-features :=
+endif
+
 ifdef DEBUG
     release :=
     TARGET_DIR := $(TARGET_DIR)/debug
@@ -19,10 +29,10 @@ endif
 build: grpc-as restful-as
 
 grpc-as:
-	cargo build --bin grpc-as $(release) --features grpc-bin
+	cargo build --bin grpc-as $(release) $(default-features) --features grpc-bin$(OPTIONAL_FEATURES)
 
 restful-as:
-	cargo build --bin restful-as $(release) --features restful-bin
+	cargo build --bin restful-as $(release) $(default-features) --features restful-bin$(OPTIONAL_FEATURES)
 
 install:
 	for bin_name in $(BIN_NAMES); do \