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+# Bootstrapped Tools
+
+All tools are statically built with the GCC 13.2.0 with musl support
+(`gcc-13.2.0-musl`). Note that dynamically linking with this compiler will not work on
+non-musl systems. Therefore, all *configure checks* and *build steps* must use
+static linking. For more information on the compilers, see
+[COMPILERS.md](./COMPILERS.md).
+
+## Busybox
+
+Busybox is compiled statically by setting `LDFLAGS='-static'`. It strictly
+requires GCC for building, which can be set via `HOSTCC` and `HOSTCXX`. It
+employs *internal checks* to verify that the compilers are working. However,
+those checks seem to ignore `LDFLAGS`, which causes them to fail on non-musl
+systems. Therefore, we had to forcefully set the compilers to `"${CC} -static"`
+and `"${CXX} -static"`.
+
+For reproducibility, we additionally had to set `SOURCE_DATE_EPOCH=0`.
+
+## Make
+
+Make is compiled statically by setting `LDFLAGS='-static'`. For some reason, the
+binary likes to record the absolute path to the C++ compiler on the build
+machine (despite not even using C++). To achieve reproducibility, we set
+`CXX='unused'`.
+
+## CMake
+
+CMake is compiled statically with bundled dependencies. The only dependency that
+is not bundled with CMake's sources is `libssl`. We use the C++ library
+`boringssl` to satisfy that dependency. However, CMake expects `libssl` to be a
+C library (not C++), which is solved via a small patch. For reproducibility, we
+had to redefine `__FILE__` to `__FILE_NAME__`, which is supported since GCC 12.
+
+## Python
+
+Python is compiled statically with default modules built in. See [Building
+Python Statically](https://wiki.python.org/moin/BuildStatically) for full
+details. Missing modules are:
+- `nis`: deprecated module that caused the static build to fail
+- `ssl`: unsupported, due to missing `libssl` C library
+
+Furthermore, the Python binary likes to record its build time and date, so we
+had to set `SOURCE_DATE_EPOCH=0` to achieve reproducibility.
+