Minor build fixes

Two changes: make some linux-specific linker options linux and linker specific.
And in the cross-compile environment, prefer the $HOME/qt/bin tools to
whatever might be somewhere else in the path.

bitcoin-qt.pro

@@ -29,19 +29,19 @@ contains(RELEASE, 1) {
 
     !win32:!macx {
         # Linux: static link
-        LIBS += -Wl,-Bstatic
+        LIBS += -Wl,-Bstatic -Wl,-z,relro -Wl,-z,now
+        # for extra security (see: https://wiki.debian.org/Hardening)
+        QMAKE_CXXFLAGS *= -D_FORTIFY_SOURCE=2
     }
 }
 
 !win32 {
-# for extra security against potential buffer overflows: enable GCCs Stack Smashing Protection
-QMAKE_CXXFLAGS *= -fstack-protector-all
-QMAKE_LFLAGS *= -fstack-protector-all
-# We need to exclude this for Windows cross compile with MinGW 4.2.x, as it will result in a non-working executable!
-# This can be enabled for Windows, when we switch to MinGW >= 4.4.x.
+    # for extra security against potential buffer overflows: enable GCCs Stack Smashing Protection
+    QMAKE_CXXFLAGS *= -fstack-protector-all
+    QMAKE_LFLAGS *= -fstack-protector-all
+    # Exclude on Windows cross compile with MinGW 4.2.x, as it will result in a non-working executable!
+    # This can be enabled for Windows, when we switch to MinGW >= 4.4.x.
 }
-# for extra security (see: https://wiki.debian.org/Hardening)
-QMAKE_CXXFLAGS *= -D_FORTIFY_SOURCE=2 -Wl,-z,relro -Wl,-z,now
 # for extra security on Windows: enable ASLR and DEP via GCC linker flags
 win32:QMAKE_LFLAGS *= -Wl,--dynamicbase -Wl,--nxcompat
 # on Windows: enable GCC large address aware linker flag

contrib/gitian-descriptors/gitian-win32.yml

@@ -24,7 +24,7 @@ script: |
   cd $HOME/qt
   unzip ../build/qt-win32-4.8.3-gitian-r1.zip
   cd $HOME/build/
-  export PATH=$PATH:$HOME/qt/bin/
+  export PATH=$HOME/qt/bin/:$PATH
   #
   mkdir boost_1_50_0
   cd boost_1_50_0