Tweak the build to support building on Yocto Thud (Azure#1196)

* Add Makefile with `make dist` to generate a source tarball

* Add flag to skip libiothsm build

* Use env::var_os

* Address review comments

Makefile

@@ -0,0 +1,47 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+TARGET=target
+
+_version:=$(shell cat edgelet/version.txt)
+VERSION?=${_version}
+REVISION?=1
+
+# Converts debian versioning to rpm version
+# deb 1.0.1~dev100 ~> rpm 1.0.1-0.1.dev100
+RPM_VERSION?=$(word 1,$(subst ~, , $(VERSION)))
+_release=$(or $(and $(word 2,$(subst ~, ,$1)),0.${REVISION}.$(word 2,$(subst ~, ,$1))),${REVISION})
+RPM_RELEASE?=$(call _release, ${VERSION})
+
+PACKAGE_NAME=iotedge
+PACKAGE="$(PACKAGE_NAME)-$(RPM_VERSION)"
+
+GIT=git
+GZIP=gzip
+MKDIR_P=mkdir -p
+
+$(TARGET):
+	$(MKDIR_P) $(TARGET)
+
+$(TARGET)/$(PACKAGE).tar.gz: $(TARGET)
+	@echo Running git archive...
+	@$(GIT) archive --prefix=$(PACKAGE)/ -o $(TARGET)/$(PACKAGE).tar $(VERSION) 2> /dev/null || (echo 'Warning: $(VERSION) does not exist.' && $(GIT) archive --prefix=$(PACKAGE)/ -o $(TARGET)/$(PACKAGE).tar HEAD)
+	@echo Running git archive submodules...
+	p=`pwd` && (echo .; git submodule foreach --recursive) | while read entering path; do \
+	    temp="$${path%\'}"; \
+	    temp="$${temp#\'}"; \
+	    path=$$temp; \
+	    [ "$$path" = "" ] && continue; \
+	    (cd $$path && $(GIT) archive --prefix=$(PACKAGE)/$$path/ HEAD > $$p/$(TARGET)/tmp.tar && tar --concatenate --file=$$p/$(TARGET)/$(PACKAGE).tar $$p/$(TARGET)/tmp.tar && rm $$p/$(TARGET)/tmp.tar); \
+	done
+	gzip -f $(TARGET)/$(PACKAGE).tar
+	rm -f $(TARGET)/$(PACKAGE).tar
+
+# Produces a tarball of the source including all git submodules
+dist: $(TARGET)/$(PACKAGE).tar.gz
+
+# Removes the build directory
+clean:
+	rm -rf $(TARGET)
+
+.PHONY: clean dist version
+

edgelet/hsm-sys/build.rs

@@ -80,7 +80,7 @@ impl SetPlatformDefines for Config {
     }
 }
 
-fn main() {
+fn build_libiothsm() {
     // Clone Azure C -shared library
     let c_shared_repo = "azure-iot-hsm-c/deps/c-shared";
     let utpm_repo = "azure-iot-hsm-c/deps/utpm";
@@ -192,3 +192,13 @@ fn main() {
     #[cfg(unix)]
     println!("cargo:rustc-link-lib=crypto");
 }
+
+fn main() {
+    if env::var_os("LIBIOTHSM_NOBUILD").is_some() {
+        // libiothsm-std is expected to be built and installed out of band
+        println!("cargo:rustc-link-lib=iothsm");
+    } else {
+        // build libiothsm-std as part of hsm-sys build
+        build_libiothsm();
+    }
+}