Turn the coverage analysis stdenv adapters into setup hooks

Stdenv adapters are kinda weird and un-idiomatic (especially when they
don't actually change stdenv).  It's more idiomatic to say

  buildInputs = [ makeCoverageAnalysisReport ];

pkgs/build-support/setup-hooks/enable-coverage-instrumentation.sh

@@ -0,0 +1,14 @@
+# Force GCC to build with coverage instrumentation.  Also disable
+# optimisation, since it may confuse things.
+export NIX_CFLAGS_COMPILE="$NIX_CFLAGS_COMPILE -O0 --coverage"
+
+# FIXME: Handle the case where postUnpack is already set.
+postUnpack() {
+    # This is an uberhack to prevent libtool from remoaving gcno
+    # files.  This has been fixed in libtool, but there are packages
+    # out there with old ltmain.sh scripts.  See
+    # http://www.mail-archive.com/libtool@gnu.org/msg10725.html
+    for i in $(find -name ltmain.sh); do
+        substituteInPlace $i --replace '*.$objext)' '*.$objext | *.gcno)'
+    done
+}

pkgs/build-support/setup-hooks/make-coverage-analysis-report.sh

@@ -0,0 +1,18 @@
+postPhases+=" coverageReportPhase"
+
+coverageReportPhase() {
+    lcov --directory . --capture --output-file app.info
+    set -o noglob
+    lcov --remove app.info $lcovFilter > app2.info
+    set +o noglob
+    mv app2.info app.info
+
+    mkdir -p $out/coverage
+    genhtml app.info $lcovExtraTraceFiles -o $out/coverage > log
+
+    # Grab the overall coverage percentage for use in release overviews.
+    mkdir -p $out/nix-support
+    grep "Overall coverage rate" log | sed 's/^.*(\(.*\)%).*$/\1/' > $out/nix-support/coverage-rate
+
+    echo "report coverage $out/coverage" >> $out/nix-support/hydra-build-products
+}