Fix "Installing from source" instructions

Fixes google#6387

Author: avagin

README.md

@@ -61,8 +61,9 @@ Make sure the following dependencies are installed:
 Build and install the `runsc` binary:
 
 ```sh
-make runsc
-sudo cp ./bazel-bin/runsc/linux_amd64_pure_stripped/runsc /usr/local/bin
+mkdir -p bin
+make copy TARGETS=runsc DESTINATION=bin/
+sudo cp ./bin/runsc /usr/local/bin
 ```
 
 ### Testing

tools/bazel.mk

@@ -186,8 +186,8 @@ build_paths = \
   (set -euo pipefail; \
   $(call wrapper,$(BAZEL) build $(BASE_OPTIONS) $(BAZEL_OPTIONS) $(1)) && \
   $(call wrapper,$(BAZEL) cquery $(BASE_OPTIONS) $(BAZEL_OPTIONS) $(1) --output=starlark --starlark:file=tools/show_paths.bzl) \
-  | xargs -r -n 1 -I {} bash -c 'test -e "{}" || exit 0; readlink -f "{}"' \
-  | xargs -r -n 1 -I {} bash -c 'set -euo pipefail; $(2)')
+  | xargs -r -I {} bash -c 'test -e "{}" || exit 0; readlink -f "{}"' \
+  | xargs -r -I {} bash -c 'set -euo pipefail; $(2)')
 
 clean = $(call header,CLEAN) && $(call wrapper,$(BAZEL) clean)
 build = $(call header,BUILD $(1)) && $(call build_paths,$(1),echo {})