synth tries to rebuild graphics/gdk-pixbuf2.
The only dependency recently updated is misc/shared-mime-info.

From the build log:
FAILED: tests/cve-2015-4491.p/meson-generated_.._resources.c.o 
cc -Itests/cve-2015-4491.p -Itests -I../tests -I. -I.. -Igdk-pixbuf -I../gdk-pixbuf -I/usr/local/include/glib-2.0 -I/usr/local/lib/glib-2.0/include -I/usr/local/include -fno-color-diagnostics -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -std=c99 -O3 -D_POSIX_C_SOURCE=200809L -D_DEFAULT_SOURCE -D_XOPEN_SOURCE -DHAVE_CONFIG_H=1 -O2 -pipe -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing -isystem /usr/local/include -pthread -Wpointer-arith -Wformat=2 -Wstrict-prototypes -Wnested-externs -Wold-style-definition -Wdeclaration-after-statement -Wunused -Wcast-align -Wmissing-noreturn -Wmissing-format-attribute -fno-strict-aliasing -Wno-int-conversion -Wno-uninitialized -Werror=implicit -Werror=nonnull -Werror=init-self -Werror=main -Werror=missing-braces -Werror=sequence-point -Werror=return-type -Werror=trigraphs -Werror=array-bounds -Werror=write-strings -Werror=address -Werror=int-to-pointer-cast -Werror=pointer-to-int-cast -Werror=empty-body -fvisibility=hidden -MD -MQ tests/cve-2015-4491.p/meson-generated_.._resources.c.o -MF tests/cve-2015-4491.p/meson-generated_.._resources.c.o.d -o tests/cve-2015-4491.p/meson-generated_.._resources.c.o -c tests/resources.c
cc: error: no such file or directory: 'tests/resources.c'
cc: error: no input files