Handle jpeg library fuzz false positives

The jpeg library has some assembly code that is missed by the compiler
instrumentation used by memory sanitization. There is a runtime
environment variable that is used to work around this issue.

fuzz/dct_fuzzer.cc

@@ -2,6 +2,7 @@
 #include <qpdf/Pl_DCT.hh>
 #include <iostream>
 #include <stdexcept>
+#include <cstdlib>
 
 class FuzzHelper
 {
@@ -46,6 +47,11 @@ FuzzHelper::run()
 
 extern "C" int LLVMFuzzerTestOneInput(unsigned char const* data, size_t size)
 {
+#ifndef _WIN32
+    // Used by jpeg library to work around false positives in memory
+    // sanitizer.
+    setenv("JSIMD_FORCENONE", "1", 1);
+#endif
     FuzzHelper f(data, size);
     f.run();
     return 0;

fuzz/qpdf_fuzzer.cc

@@ -9,6 +9,7 @@
 #include <qpdf/QPDFPageLabelDocumentHelper.hh>
 #include <qpdf/QPDFOutlineDocumentHelper.hh>
 #include <qpdf/QPDFAcroFormDocumentHelper.hh>
+#include <cstdlib>
 
 class DiscardContents: public QPDFObjectHandle::ParserCallbacks
 {
@@ -223,6 +224,11 @@ FuzzHelper::run()
 
 extern "C" int LLVMFuzzerTestOneInput(unsigned char const* data, size_t size)
 {
+#ifndef _WIN32
+    // Used by jpeg library to work around false positives in memory
+    // sanitizer.
+    setenv("JSIMD_FORCENONE", "1", 1);
+#endif
     FuzzHelper f(data, size);
     f.run();
     return 0;

libqpdf/Pl_DCT.cc

@@ -8,6 +8,7 @@
 #include <stdexcept>
 #include <stdlib.h>
 #include <string>
+#include <cstring>
 
 #if BITS_IN_JSAMPLE != 8
 # error "qpdf does not support libjpeg built with BITS_IN_JSAMPLE != 8"