Failing to build in provided Docker environment

[sempervictus]

Running into an inability to build mettle bins anymore, even in the Docker environment built from this repo:

make all
...
libtool: warning: undefined symbols not allowed in i686-w64-mingw32 shared libraries; building static only
Configuring mettle for i686-w64-mingw32
configure: WARNING: unrecognized options: --disable-shared
configure: error: cannot find install-sh, install.sh, or shtool in "/mettle/mettle" "/mettle/mettle/.." "/mettle/mettle/../.."
make/Makefile.mettle:61: recipe for target '/mettle/build/i686-w64-mingw32/mettle/Makefile' failed
make[1]: *** [/mettle/build/i686-w64-mingw32/mettle/Makefile] Error 1
make[1]: Leaving directory '/mettle'
Makefile:33: recipe for target 'i686-w64-mingw32.build' failed
make: *** [i686-w64-mingw32.build] Error 2

[sempervictus]

Not a MinGW issue:

Configuring libev for x86_64-linux-musl
Building libev for x86_64-linux-musl
Unpacking libsigar for x86_64-linux-musl
Configuring libsigar for x86_64-linux-musl
Building libsigar for x86_64-linux-musl
Unpacking libdnet for x86_64-linux-musl
Configuring libdnet for x86_64-linux-musl
Building libdnet for x86_64-linux-musl
Configuring mettle for x86_64-linux-musl
configure: WARNING: unrecognized options: --disable-shared
configure: error: cannot find install-sh, install.sh, or shtool in "/mettle/mettle" "/mettle/mettle/.." "/mettle/mettle/../.."
make/Makefile.mettle:61: recipe for target '/mettle/build/x86_64-linux-musl/mettle/Makefile' failed
make[1]: *** [/mettle/build/x86_64-linux-musl/mettle/Makefile] Error 1
make[1]: Leaving directory '/mettle'
Makefile:33: recipe for target 'x86_64-linux-musl.build' failed
make: *** [x86_64-linux-musl.build] Error 2