package does not build reproducibly

While working on the reproducible builds effort, I found that
when building the qutim package for openSUSE Linux, there were slight differences between each build in several .so files like

/usr/lib64/qutim/plugins/libsdlsound.so differs in ELF section .rodata
--- /tmp/tmp.yl865OqfE2/tmp.KPxqyhEYIe 2017-09-23 15:43:47.779396435 +0000
+++ /tmp/tmp.yl865OqfE2/tmp.podTPZ6puH 2017-09-23 15:43:47.783396458 +0000
@@ -14,8 +14,8 @@
  58f0 204c6179 65720000 70617474 65726e3d Layer..pattern=
  5900 51555449 4d5f504c 5547494e 5f564552 QUTIM_PLUGIN_VER
  5910 49464943 4154494f 4e5f4441 54410a64 IFICATION_DATA.d
- 5920 65627567 69643d39 34613864 39313536 ebugid=94a8d9156
- 5930 36386634 3436370a 6c696271 7574696d 68f4467.libqutim
+ 5920 65627567 69643d62 38636534 36353136 ebugid=b8ce46516
+ 5930 30663162 3734350a 6c696271 7574696d 0f1b745.libqutim
  5940 3d302e33 2e332e30 00000000 00000000 =0.3.3.0........

coming from
+++ /home/abuild/rpmbuild/BUILD/qutim-0.3.3/build/CMakeCache.txt 2018-11-14 02:16:42.249233141 +0000
@@ -3128,97 +3128,97 @@
 QUTIM_ADDITIONAL_SOURCES:INTERNAL=
 QUTIM_INCLUDE_DIR:INTERNAL=/home/abuild/rpmbuild/BUILD/qutim-0.3.3/build/core/libqutim/include
 QUTIM_LIBRARY:INTERNAL=libqutim
-QUTIM_accountcreator_DEBUG_ID:INTERNAL=857d7147e841e0e7
-QUTIM_addcontactdlg_DEBUG_ID:INTERNAL=4184d813f2f957ce

coming from core/cmake/QutIMMacros.cmake using RANDOM

IMHO the usage of RANDOM should be replaced with a hash over the relevant input
so that it changes if and only if that input changes.