Remove uncessary srcs entries in pkg_tars. (#129)

This incorrectly copies the revision.bzl files into the container.
diff --git a/third_party/clang/BUILD b/third_party/clang/BUILD
index 10fdc27..1e73424 100644
--- a/third_party/clang/BUILD
+++ b/third_party/clang/BUILD
@@ -26,10 +26,6 @@
 
 pkg_tar(
     name = "debian8_tar",
-    srcs = glob(
-        ["**/*"],
-        exclude = ["**/BUILD"],
-    ),
     package_dir = "/usr/local/",
     strip_prefix = ".",
     tags = ["manual"],
@@ -40,10 +36,6 @@
 
 pkg_tar(
     name = "debian9_tar",
-    srcs = glob(
-        ["**/*"],
-        exclude = ["**/BUILD"],
-    ),
     package_dir = "/usr/local/",
     strip_prefix = ".",
     tags = ["manual"],
@@ -54,10 +46,6 @@
 
 pkg_tar(
     name = "ubuntu16_04_tar",
-    srcs = glob(
-        ["**/*"],
-        exclude = ["**/BUILD"],
-    ),
     package_dir = "/usr/local/",
     strip_prefix = ".",
     tags = ["manual"],
diff --git a/third_party/golang/BUILD b/third_party/golang/BUILD
index 121a64b..4715a4e 100644
--- a/third_party/golang/BUILD
+++ b/third_party/golang/BUILD
@@ -25,10 +25,6 @@
 
 pkg_tar(
     name = "tar",
-    srcs = glob(
-        ["**/*"],
-        exclude = ["**/BUILD"],
-    ),
     package_dir = "/usr/local/",
     strip_prefix = ".",
     tags = ["manual"],
diff --git a/third_party/libcxx/BUILD b/third_party/libcxx/BUILD
index 2e0979d..c1b94b2 100644
--- a/third_party/libcxx/BUILD
+++ b/third_party/libcxx/BUILD
@@ -26,10 +26,6 @@
 
 pkg_tar(
     name = "debian8_tar",
-    srcs = glob(
-        ["**/*"],
-        exclude = ["**/BUILD"],
-    ),
     package_dir = "/usr/local/",
     strip_prefix = ".",
     tags = ["manual"],
@@ -40,10 +36,6 @@
 
 pkg_tar(
     name = "debian9_tar",
-    srcs = glob(
-        ["**/*"],
-        exclude = ["**/BUILD"],
-    ),
     package_dir = "/usr/local/",
     strip_prefix = ".",
     tags = ["manual"],
@@ -54,10 +46,6 @@
 
 pkg_tar(
     name = "ubuntu16_04_tar",
-    srcs = glob(
-        ["**/*"],
-        exclude = ["**/BUILD"],
-    ),
     package_dir = "/usr/local/",
     strip_prefix = ".",
     tags = ["manual"],