OT: It's never done *this* before

In the midst of yet another long, tedious Qt5-Base build, this happened:

g++ -c -fno-keep-inline-dllexport -D_GNU_SOURCE -pipe -ggdb -O2 -pipe 
-Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=3 
-fstack-protector-strong --param=ssp-buffer-size=4 -Werror=return-type 
-Wno-deprecated-declarations -fno-delete-null-pointer-checks 
-ffile-prefix-map=/usr/src/qt5-base-5.15.16/qt5-base-5.15.16-1.x86_64/build=/usr/src/debug/qt5-base-5.15.16-1 
-ffile-prefix-map=/usr/src/qt5-base-5.15.16/qt5-base-5.15.16-1.x86_64/src/qtbase-everywhere-src-5.15.16=/usr/src/debug/qt5-base-5.15.16-1 
-fno-exceptions -Wall -Wextra -D_REENTRANT -DQT_NO_LINKED_LIST 
-DQT_NO_JAVA_STYLE_ITERATORS -DQT_NO_EXCEPTIONS -DQT_NO_DEBUG 
-DQT_GUI_LIB -DQT_CORE_LIB 
-I/usr/src/qt5-base-5.15.16/qt5-base-5.15.16-1.x86_64/src/qtbase-everywhere-src-5.15.16/examples/qpa/qrasterwindow 
-I. 
-I/usr/src/qt5-base-5.15.16/qt5-base-5.15.16-1.x86_64/src/qtbase-everywhere-src-5.15.16/include 
-I/usr/src/qt5-base-5.15.16/qt5-base-5.15.16-1.x86_64/src/qtbase-everywhere-src-5.15.16/include/QtGui 
-I../../../include -I../../../include/QtGui 
-I/usr/src/qt5-base-5.15.16/qt5-base-5.15.16-1.x86_64/src/qtbase-everywhere-src-5.15.16/include/QtCore 
-I../../../include/QtCore -I.moc 
-I/usr/src/qt5-base-5.15.16/qt5-base-5.15.16-1.x86_64/src/qtbase-everywhere-src-5.15.16/mkspecs/cygwin-g++ 
-o .obj/main.o 
/usr/src/qt5-base-5.15.16/qt5-base-5.15.16-1.x86_64/src/qtbase-everywhere-src-5.15.16/examples/qpa/qrasterwindow/main.cpp 
                          In file included from 
/usr/src/qt5-base-5.15.16/qt5-base-5.15.16-1.x86_64/src/qtbase-everywhere-src-5.15.16/examples/qpa/qrasterwindow/main.cpp:51:
./QRasterWindow:1:3: error: stray â<80><98>\220â<80><99> in program
     1 | 
MZ<90><U+0000><U+0003><U+0000><U+0000><U+0000><U+0004><U+0000><U+0000>
<U+0000><ff><ff><U+0000><U+0000><b8><U+0000><U+0000><U+0000><U+0000>
<U+0000><U+0000><U+0000>@<U+0000><U+0000><U+0000><U+0000><U+0000>
<U+0000><U+0000><U+0000><U+0000><U+0000><U+0000><U+0000><U+0000>
<U+0000><U+0000><U+0000><U+0000><U+0000><U+0000><U+0000><U+0000><U+0000>
<U+0000><U+0000><U+0000><U+0000><U+0000><U+0000><U+0000><U+0000><U+0000>
<U+0000><U+0000><U+0000><U+0000><80><U+0000><U+0000><U+0000><U+000E>
<U+001F><ba><U+000E><U+0000><b4> <cd>!<b8><U+0001>L<cd>!This program 
cannot be run in DOS mode.
       |   ^~~~

And so on for another 136,454 error messages. Somehow g++ has ingested 
an executable file via #include; the leading "MZ" is evidence.

Crossed-up file descriptor(s) somewhere?  Does this count as a DoS?
Rhetorically,

..mark