From https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.fyi%2FLibfuzzer_Upload_Linux_MSan%2F3728%2F%2B%2Frecipes%2Fsteps%2Fcompile%2F0%2Fstdout:

FAILED: obj/third_party/pdfium/fpdfxfa/cpdfxfa_context.o 
../../third_party/llvm-build/Release+Asserts/bin/clang++ -MMD -MF obj/third_party/pdfium/fpdfxfa/cpdfxfa_context.o.d -DV8_DEPRECATION_WARNINGS -DUSE_UDEV -DUSE_AURA=1 -DUSE_PANGO=1 -DUSE_CAIRO=1 -DUSE_GLIB=1 -DUSE_NSS_CERTS=1 -DUSE_X11=1 -DNO_TCMALLOC -DMEMORY_TOOL_REPLACES_ALLOCATOR -DMEMORY_SANITIZER_INITIAL_SIZE -DMEMORY_SANITIZER -DDISABLE_NACL -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DCHROMIUM_BUILD -DENABLE_MEDIA_ROUTER=1 -DFIELDTRIAL_TESTING_ENABLED -DCR_CLANG_REVISION=\"298539-1\" -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -DSANITIZER_COVERAGE -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DV8_DEPRECATION_WARNINGS -D_FX_CPU_=_FX_X64_ -DOPJ_STATIC -DPNG_PREFIX -DPNG_USE_READ_MACROS -DPDF_ENABLE_V8 -DPDF_ENABLE_XFA -DPDF_ENABLE_XFA_BMP -DPDF_ENABLE_XFA_GIF -DPDF_ENABLE_XFA_PNG -DPDF_ENABLE_XFA_TIFF -DPDFIUM_PRINT_TEXT_WITH_GDI -I../.. -Igen -I../../third_party/pdfium -I../../build/linux/debian_wheezy_amd64-sysroot/usr/include/freetype2 -I../../v8/include -Igen/v8/include -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -funwind-tables -fPIC -pipe -B../../third_party/binutils/Linux_x64/Release/bin -fcolor-diagnostics -m64 -march=x86-64 -pthread -Wall -Werror -Wextra -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-covered-switch-default -Wno-deprecated-register -Wno-unneeded-internal-declaration -Wno-inconsistent-missing-override -Wno-shift-negative-value -Wno-undefined-var-template -Wno-nonportable-include-path -Wno-address-of-packed-member -Wno-unused-lambda-capture -Wno-user-defined-warnings -O1 -fno-ident -fdata-sections -ffunction-sections -fno-omit-frame-pointer -g1 --sysroot=../../build/linux/debian_wheezy_amd64-sysroot -gline-tables-only -gcolumn-info -fno-omit-frame-pointer -fsanitize-coverage=trace-pc-guard -mllvm -sanitizer-coverage-prune-blocks=1 -fsanitize=memory -fsanitize-memory-track-origins=2 -fsanitize-blacklist=../../tools/msan/blacklist.txt -fvisibility=hidden -Xclang -load -Xclang ../../third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so -Xclang -add-plugin -Xclang find-bad-constructs -Xclang -plugin-arg-find-bad-constructs -Xclang check-auto-raw-pointer -Xclang -plugin-arg-find-bad-constructs -Xclang check-ipc -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -fPIC -fvisibility-inlines-hidden -std=gnu++11 -fno-rtti -nostdinc++ -isystem../../buildtools/third_party/libc++/trunk/include -isystem../../buildtools/third_party/libc++abi/trunk/include -fno-exceptions -c ../../third_party/pdfium/fpdfsdk/fpdfxfa/cpdfxfa_context.cpp -o obj/third_party/pdfium/fpdfxfa/cpdfxfa_context.o
In file included from ../../third_party/pdfium/fpdfsdk/fpdfxfa/cpdfxfa_context.cpp:23:
In file included from ../../third_party/pdfium/xfa/fxfa/cxfa_deffontmgr.h:14:
In file included from ../../third_party/pdfium/xfa/fgas/font/cfgas_gefont.h:16:
In file included from ../../third_party/pdfium/xfa/fgas/font/cfgas_fontmgr.h:21:
../../third_party/pdfium/third_party/freetype/include/freetype/fttypes.h:354:19: error: redefinition of 'FT_UnitVector_'
  typedef struct  FT_UnitVector_
                  ^
../../build/linux/debian_wheezy_amd64-sysroot/usr/include/freetype2/freetype/fttypes.h:350:19: note: previous definition is here
  typedef struct  FT_UnitVector_
                  ^
In file included from ../../third_party/pdfium/fpdfsdk/fpdfxfa/cpdfxfa_context.cpp:23:
In file included from ../../third_party/pdfium/xfa/fxfa/cxfa_deffontmgr.h:14:
In file included from ../../third_party/pdfium/xfa/fgas/font/cfgas_gefont.h:16:
In file included from ../../third_party/pdfium/xfa/fgas/font/cfgas_fontmgr.h:21:
../../third_party/pdfium/third_party/freetype/include/freetype/fttypes.h:385:19: error: redefinition of 'FT_Matrix_'
  typedef struct  FT_Matrix_
                  ^
../../build/linux/debian_wheezy_amd64-sysroot/usr/include/freetype2/freetype/fttypes.h:381:19: note: previous definition is here
  typedef struct  FT_Matrix_
                  ^
In file included from ../../third_party/pdfium/fpdfsdk/fpdfxfa/cpdfxfa_context.cpp:23:
In file included from ../../third_party/pdfium/xfa/fxfa/cxfa_deffontmgr.h:14:
In file included from ../../third_party/pdfium/xfa/fgas/font/cfgas_gefont.h:16:
In file included from ../../third_party/pdfium/xfa/fgas/font/cfgas_fontmgr.h:21:
../../third_party/pdfium/third_party/freetype/include/freetype/fttypes.h:406:19: error: redefinition of 'FT_Data_'
  typedef struct  FT_Data_

thestig@, does this look like it was caused by https://chromium.googlesource.com/chromium/src/+/15bd8b5cbe93ed44c92b4108ef561ac278b91490 ?