Compile Xdebug with the "./rebuild.sh" script with GCC 8 installed.

Result:

<pre>
cc -g -O0 -Wall -Wdeclaration-after-statement -Wdiscarded-qualifiers -Wempty-body -Wenum-compare -Werror -Wextra -Wimplicit-fallthrough -Winit-self -Wlogical-not-parentheses -Wlogical-op -Wmaybe-uninitialized -Wmissing-format-attribute -Wno-missing-field-initializers -Wno-sign-compare -Wno-unused-but-set-variable -Wno-unused-parameter -Wno-variadic-macros -Wparentheses -Wsizeof-array-argument -Wwrite-strings -fdiagnostics-show-option -fno-exceptions -fno-omit-frame-pointer -fno-optimize-sibling-calls -fstack-protector -I. -I/home/derick/dev/php/xdebug-xdebug -DPHP_ATOM_INC -I/home/derick/dev/php/xdebug-xdebug/include -I/home/derick/dev/php/xdebug-xdebug/main -I/home/derick/dev/php/xdebug-xdebug -I/usr/local/php/7.3dev/include/php -I/usr/local/php/7.3dev/include/php/main -I/usr/local/php/7.3dev/include/php/TSRM -I/usr/local/php/7.3dev/include/php/Zend -I/usr/local/php/7.3dev/include/php/ext -I/usr/local/php/7.3dev/include/php/ext/date/lib -DHAVE_CONFIG_H -g -O0 -c /home/derick/dev/php/xdebug-xdebug/xdebug_handler_dbgp.c -fPIC -DPIC -o .libs/xdebug_handler_dbgp.o
/home/derick/dev/php/xdebug-xdebug/xdebug_compat.c: In function ‘xdebug_addslashes’:
/home/derick/dev/php/xdebug-xdebug/xdebug_compat.c:276:15: error: this statement may fall through [-Werror=implicit-fallthrough=]
*target++ = '\';

/home/derick/dev/php/xdebug-xdebug/xdebug_compat.c:278:4: note: here
    default:
    ^~~~~~~
cc1: all warnings being treated as errors
make: *** [Makefile:234: xdebug_compat.lo] Error 1
make: *** Waiting for unfinished jobs....
</pre>