build: fixed SKIP_SERVER_RUST not respected

Fixes #1056

Co-authored-by: MohammadAliAfsahi <35253602+MohammadAliAfsahi@users.noreply.github.com>

Makefile

@@ -44,11 +44,13 @@ build: aw-core/.git
 #	needed due to https://github.com/pypa/setuptools/issues/1963
 #	would ordinarily be specified in pyproject.toml, but is not respected due to https://github.com/pypa/setuptools/issues/1963
 	pip install 'setuptools>49.1.1'
-	@if (which cargo); then \
-		echo 'Rust found!'; \
-	else \
-		echo 'ERROR: Rust not found, try running with SKIP_SERVER_RUST=true'; \
-		exit 1; \
+	@if [ "$(SKIP_SERVER_RUST)" = "false" ]; then \
+		if (which cargo); then \
+			echo 'Rust found!'; \
+		else \
+			echo 'ERROR: Rust not found, try running with SKIP_SERVER_RUST=true'; \
+			exit 1; \
+		fi \
 	fi
 	for module in $(SUBMODULES); do \
 		echo "Building $$module"; \