Bug#644764: FTBFS: asm/errno.h: No such file or directory (due to multiarch)

[Kyle Moffett <Kyle.D.Moffett@boeing.com>]

Source: gcc-4.6
Version: 4.6.1-13
Severity: serious
Justification: fails to build from source (but built successfully in the past)

When trying to rebuild gcc-4.6 natively from source, I get build
failures of the following variety:
  asm/errno.h: No such file or directory

In particular, it seems that recent linux-libc-dev packages have moved
the architecture-specific header files from the path "/usr/include/asm"
to "/usr/include/x86_64-linux-gnu/asm".

In particular, I have linux-libc-dev 3.0.0-3 installed locally.

The existing "gcc" on the system finds files in that search path, but
when building libgcc it seems that the temporary built "xgcc" does not.
You can some one example failed command below.

Cheers,
Kyle Moffett

Failed command:
/srv/stuff/toolchain/STAGE2/GCC/gcc-4.6-4.6.1/build/./gcc/xgcc	\
  -B/srv/stuff/toolchain/STAGE2/GCC/gcc-4.6-4.6.1/build/./gcc/	\
  -B/usr/x86_64-linux-gnu/bin/ -B/usr/x86_64-linux-gnu/lib/	\
  -isystem /usr/x86_64-linux-gnu/include			\
  -isystem /usr/x86_64-linux-gnu/sys-include			\
  -g -O2 -m32 -O2  -g -O2 -DIN_GCC -W -Wall -Wwrite-strings	\
  -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes		\
  -Wold-style-definition -isystem ./include  -fPIC -g		\
  -DHAVE_GTHR_DEFAULT -DIN_LIBGCC2 -D__GCC_FLOAT_NOT_NEEDED	\
  -fno-stack-protector -I. -I. -I../../.././gcc			\
  -I../../../../src/libgcc					\
  -I../../../../src/libgcc/.					\
  -I../../../../src/libgcc/../gcc				\
  -I../../../../src/libgcc/../include				\
  -I../../../../src/libgcc/config/libbid			\
  -DENABLE_DECIMAL_BID_FORMAT -DHAVE_CC_TLS -DUSE_TLS		\
  -o _muldi3.o -MT _muldi3.o -MD -MP -MF _muldi3.dep -DL_muldi3	\
  -c ../../../../src/libgcc/../gcc/libgcc2.c			\
  -fvisibility=hidden -DHIDE_EXPORTS

Error output:
  In file included from /usr/include/bits/errno.h:25:0,
                   from /usr/include/errno.h:36,
                   from ../../../../src/libgcc/../gcc/tsystem.h:93,
                   from ../../../../src/libgcc/../gcc/libgcc2.c:29:
  /usr/include/linux/errno.h:4:23: fatal error: asm/errno.h: No such file or directory

-- System Information:
Debian Release: wheezy/sid
  APT prefers testing
  APT policy: (700, 'testing'), (700, 'stable'), (600, 'unstable'), (500, 'stable-updates'), (500, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 3.0.0-1-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash