I'm building gcc 11.2.0 to be the system compiler for my current system (Ubuntu 21, using gcc 9.3) and an LFS system that will reside on another device. When building with --enable-languages=all, the bootstrap failed for ambiguous reasons; to simplify (at the cost of time, of course), I started over, this time targeting the languages piecemeal.

The first run consisted of the C, C++, and Objective-C frontends and this was successful. Next, I moved on to the Fortran frontend. While compilation appeared successful, it failed to install with the following:

g++ -std=c++11 -c   -g -O2 -DIN_GCC     -fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wno-error=format-diag -Wmissing-format-attribute -Woverloaded-virtual -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings   -DHAVE_CONFIG_H  -DGENERATOR_FILE -fno-PIE -I. -Ibuild -I../../gcc-11.2.0/gcc -I../../gcc-11.2.0/gcc/build -I../../gcc-11.2.0/gcc/../include  -I../../gcc-11.2.0/gcc/../libcpp/include  \
    -o build/genmddeps.o ../../gcc-11.2.0/gcc/genmddeps.c
cc1plus: error: ‘-Werror=format-diag’: no option -Wformat-diag

The build was configured with: ../gcc-11.2.0/configure --prefix=/usr --disable-multilib --enable-shared --enable-static --enable-languages=fortran --enable-default-pie --with-pic --disable-nls --enable-lto --enable-libssp --enable-libatomic --enable-libgomp --disable-libvtv

The install was attempted with: make DESTDIR=/usr/etc/sys-gcc install

I attempted to build/install twice: the first was after building the C-family targets without cleaning the directory, while the second was performed in a fresh directory. Both builds were completed with no errors, but both generated the same error when I attempted to install them to my staging point (DESTDIR).

I have two questions:

1. Why did this occur?
2. How may I fix it?

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UPDATE

The problem appeared to resolve itself this morning after a full system restart. I don't know why this would have an effect... Memory issues, perhaps? Regardless, I'll mark this as closed, but if anyone can explain the odd behavior I'd like to hear it.