I just tried to build Swift on Ubuntu 10.04 and it failed with an error message 'autoreconf: command not found'. It seems this comes with the autoconf module.
According to https://github.com/apple/swift/#system-requirements the requirements for installing includes:
sudo apt-get install git cmake ninja-build clang python uuid-dev libicu-dev icu-devtools libbsd-dev libedit-dev libxml2-dev libsqlite3-dev swig libpython-dev libncurses5-dev pkg-config libblocksruntime-dev libcurl4-openssl-dev
This doesn't include autoconf, and as such, falls over here. Should the documentation be updated to require autoconf, or should the libdispatch code not require autoconf in the first place?
libdispatch: using gold linker
+ mkdir -p /build/Ninja-ReleaseAssert/libdispatch-linux-x86_64
+ pushd //swift-corelibs-libdispatch
+ autoreconf -fvi
/swift/utils/build-script-impl: line 274: autoreconf: command not found
swift/utils/build-script: fatal error: command terminated with a non-zero exit status 127, aborting