smalltown -> metropolis

This pass removes all mentions of Smalltown, both from code and comments,
and replaces them with appropriate new terminology.

Test Plan: Refactor, covered by CI.

X-Origin-Diff: phab/D674
GitOrigin-RevId: 04a94d44ef07d46f7821530da5614daefe16d7ea
diff --git a/build/toolchain/BUILD b/build/toolchain/BUILD
index 78c4ae6..541f011 100644
--- a/build/toolchain/BUILD
+++ b/build/toolchain/BUILD
@@ -7,8 +7,9 @@
 #  - //build/toolchain:host_cc_suite , which is a fully unhermetic host toolchain,
 #    that can be used to build tools for the host.
 #  - //build/toolchain/musl-host-gcc:musl_host_cc_suite , which combines the host's
-#    gcc compiler with a sysroot tarball that targets Smalltown. This can be used to
-#    build C libraries/tools for Smalltown.
+#    gcc compiler with a sysroot tarball that targets the Metropolis node
+#    runtime. This can be used to build C libraries/tools running within the
+#    Metropolis node image.
 #
 
 # This file defines //build/toolchain:host_cc_suite.
@@ -28,8 +29,8 @@
 # toolchain that's built locally, or downloaded from the Internet - as
 # github.com/bazelbuild/bazel-toolchains does it. As that's being built, we
 # should then also have another toolchain definition for C binaries that
-# target Smalltown static binaries, so that mkfs.xfs can be built using native
-# cc_* rules, too.
+# target static binaries for Metropolis nodes, so that mkfs.xfs can be built
+# using native cc_* rules, too.
 #
 # This, and :cc_toolchain_config.bzl is based on the following tutorial:
 # https://docs.bazel.build/versions/master/tutorial/cc-toolchain-config.html
diff --git a/build/toolchain/musl-host-gcc/BUILD b/build/toolchain/musl-host-gcc/BUILD
index 95a59f6..561e311 100644
--- a/build/toolchain/musl-host-gcc/BUILD
+++ b/build/toolchain/musl-host-gcc/BUILD
@@ -3,8 +3,8 @@
 # This file defines //build/toolchain/musl-host-gcc:musl_host_cc_suite.
 #
 # This is a C++ toolchain that uses GCC from the host at hardcoded paths, with
-# a pre-built sysroot tarball that targets Smalltown with musl and Linux headers.
-# It's a superset of //build/toolchain:host_cc_suite.
+# a pre-built sysroot tarball that targets Metropolis nodes with musl and Linux
+# headers.  It's a superset of //build/toolchain:host_cc_suite.
 # For more information, see README.md.
 
 cc_toolchain_suite(
diff --git a/build/toolchain/musl-host-gcc/README.md b/build/toolchain/musl-host-gcc/README.md
index 585bac2..5154107 100644
--- a/build/toolchain/musl-host-gcc/README.md
+++ b/build/toolchain/musl-host-gcc/README.md
@@ -3,7 +3,7 @@
 
 musl-host-gcc is a Bazel C++ toolchain that uses the machine's host gcc in combination with a pre-built musl, musl headers, and Linux headers.
 
-It is currently used to build the few C binaries we need in Smalltown' runtime.
+It is currently used to build the few C binaries we need on Metropolis nodes.
 
 At some point, this toolchain should be replaced by a fully hermetic toolchain that doesn't depend on the host environment.
 
@@ -19,7 +19,7 @@
 Building Toolchain Sysroot Tarball
 ----------------------------------
 
-The toolchain's musl/linux components are currently built ahead of time and committed to this repository as `//build/toolchain/musl-host-gcc/toolchain.tar.xz`. This is the 'sysroot' tarball, that contains all headers and libraries required to build against Smalltown.
+The toolchain's musl/linux components are currently built ahead of time and committed to this repository as `//build/toolchain/musl-host-gcc/toolchain.tar.xz`. This is the 'sysroot' tarball, that contains all headers and libraries required to build for Metropolis nodes.
 
 To build this tarball, run the following commands:
 
@@ -31,7 +31,7 @@
 
 The toolchain is implemented in the following way:
 
-1. `//build/toolchain/musl-host-gcc/sysroot` is used to build `//build/toolchain/musl-host-gcc/sysroot.tar.xz` which is a tarball that contains all include and binary library files for building against musl for Smalltown (x86\_64 / k8) - thes are musl headers, musl libraries, and linux headers. This tarball is commited to source control.
+1. `//build/toolchain/musl-host-gcc/sysroot` is used to build `//build/toolchain/musl-host-gcc/sysroot.tar.xz` which is a tarball that contains all include and binary library files for building against musl for Metropolis nodes (x86\_64 / k8) - thes are musl headers, musl libraries, and linux headers. This tarball is commited to source control.
 1. When building a target that uses the toolchain, the `sysroot.tar.xz` tarball is extracted into an external repository `@musl_sysroot`, via `sysroot.bzl` and `sysroot_repository.bzl`.
 1. A toolchain config is built using `//build/toolchain:cc_toolchain_config.bzl`, which points at `gcc-wrapper.sh` as its gcc entrypoint. `gcc-wrapper.sh` expects to be able to call the host gcc with `musl.spec`.
 1. A toolchain is built in `//build/toolchain/musl-host-gcc:musl_host_cc_suite`, which uses the previously mentioned config, and builds it to contain `gcc-wrapper.sh`, `musl.spec`, and the sysroot tarball.
diff --git a/build/toolchain/musl-host-gcc/sysroot/tarball.bzl b/build/toolchain/musl-host-gcc/sysroot/tarball.bzl
index 4f12049..5466690 100644
--- a/build/toolchain/musl-host-gcc/sysroot/tarball.bzl
+++ b/build/toolchain/musl-host-gcc/sysroot/tarball.bzl
@@ -22,7 +22,7 @@
 """
 Build a sysroot-style tarball containing musl/linux headers and libraries.
 
-This can then be used to build a C toolchain that builds for Smalltown.
+This can then be used to build a C toolchain that builds C/C++ binaries for Metropolis nodes.
 """
 
 def _musl_gcc_tarball(ctx):