Include race condition binary target.

The race condition binary target is special in that it needs to
explicitly link against the dependent libraries and recompile the CGO
bindings.  Because of this, we have a new build target that produces
these binaries.

Makefile

@@ -23,6 +23,9 @@ advice:
 binary: build
 	go build -o prometheus $(BUILDFLAGS) .
 
+race_condition_binary: build
+	CGO_CFLAGS="-I$(PWD)/build/root/include" CGO_LDFLAGS="-L$(PWD)/build/root/lib" go build -race -o prometheus $(BUILDFLAGS) .
+
 build: preparation config model tools web
 
 clean:
@@ -79,4 +82,4 @@ tools:
 web: preparation config model
 	$(MAKE) -C web
 
-.PHONY: advice binary build clean config documentation format model package preparation run search_index source_path test tools
+.PHONY: advice binary build clean config documentation format model package preparation race_condition_binary run search_index source_path test tools

Makefile.INCLUDE

@@ -55,7 +55,9 @@ APT_GET_INSTALL := sudo apt-get install -y
 BREW_INSTALL := brew install
 # By default, wget sets the creation time to match the server's, which throws
 # off Make.  :-(
-WGET := wget --no-use-server-timestamps -c
+#
+# Set WGET_OPTIONS to include ``--no-use-server-timestamps`` to alleviate this.
+WGET := wget $(WGET_OPTIONS) -c
 
 REV        := $(shell git rev-parse --short HEAD)
 BRANCH     := $(shell git rev-parse --abbrev-ref HEAD)