The generated to level Makefile looks it lost its first 30 or so lines and of course is no longer a valid Makefile:
Makefile:1: *** recipe commences before first target. Stop.
Steps to Reproduce:
1. Point /bin/sh to 'dash' (setting CONFIG_SHELL in make.conf is not even needed)
2. emerge -1 ncurses
I tried putting an "eautoreconf" call in the src_prepare() prepare phase, but that fails as ncurses' configure.in uses custom macros (AC_DIVERT_HELP) that are not shipped. Digging around, it seems that those macros are only available as autoconf patches on Thomas E. Dickey's autoconf page .
For now, the usual tricks are not working :(
 http://invisible-island.net/autoconf/autoconf.html (search for AC_DIVERT_HELP there)
*** This bug has been marked as a duplicate of bug 545532 ***