Do not add weird GCC CFLAGS when using ccc-analyzer

ccc-analyzer uses both gcc and clang commands to analyze code.
The check for the flags seem to not trigger clang to be called; possibly
because the function is empty.

Belonging to [master]:
  - #2688

Author: sjoelund

configure.ac

@@ -198,17 +198,21 @@ LIBS="$LIBS_BEFORE"
 
 TRY_FLAGS="-fno-stack-protector"
 
-# GCC 5.x generates bad code due to detecting some impure functions as pure
-if $CC --version | grep -q gcc && $CC -dumpversion | grep -q "^5"; then
-  TRY_FLAGS="$TRY_FLAGS -fno-ipa-pure-const"
-fi
+if echo $CC | grep -v ccc-analyzer; then # ccc-analyzer calls gcc first and then clang; the CFLAGS need to work in both compilers...
+
+  # GCC 5.x generates bad code due to detecting some impure functions as pure
+  if $CC --version | grep -q gcc && $CC -dumpversion | grep -q "^5"; then
+    TRY_FLAGS="$TRY_FLAGS -fno-ipa-pure-const"
+  fi
+
+  # GCC 7.x issues:
+  # - RUNPATH instead of RPATH, disable that via -Wl,--disable-new-dtags
+  # - sqrt from libcolamd is not found in -lm if -Wl,--no-as-needed is not specified
+  if $CC --version | grep -q gcc && $CC -dumpversion | grep -q "^7"; then
+    TRY_FLAGS="$TRY_FLAGS -Wl,--no-as-needed"
+    RPATH_EXTRA="-Wl,--disable-new-dtags"
+  fi
 
-# GCC 7.x issues:
-# - RUNPATH instead of RPATH, disable that via -Wl,--disable-new-dtags
-# - sqrt from libcolamd is not found in -lm if -Wl,--no-as-needed is not specified
-if $CC --version | grep -q gcc && $CC -dumpversion | grep -q "^7"; then
-  TRY_FLAGS="$TRY_FLAGS -Wl,--no-as-needed"
-  RPATH_EXTRA="-Wl,--disable-new-dtags"
 fi
 
 AC_MSG_CHECKING([for flags to append to CFLAGS ($TRY_FLAGS)])