BUG: export minimal compiler flags for VTK, ParaView (fixes #44)

- in 1906, we changed the handling of compiler flags to include the
  exact values as used by OpenFOAM.

  While this is needed for compiling some external programs -- see
  https://develop.openfoam.com/Development/OpenFOAM-plus/issues/1256
  for the discussion -- it appears to bring in flags that upset
  some of the ParaView (and possibly VTK) compilation.

  The culprits are likely to be found in the various '-W' switches,
  but for now we simply extract a mininal set of compiler flags
  that include -std=c++11 -m64 -fPIC, but no optimization flags,
  additional warnings flags or OpenFOAM-specific defines.

etc/tools/ThirdPartyFunctions

@@ -55,13 +55,51 @@ fi
 
 unset BUILD_SUFFIX
 #------------------------------------------------------------------------------
+# Service routine to strip out OpenFOAM-specific portions from the compiler
+# flags (ie, everything after "-DOPENFOAM=...") while retaining '-fPIC'
+#
+stripCompilerFlags()
+{
+    local input="$@"
+    local flags="${input%-DOPENFOAM=*}"  # Strip out OpenFOAM-specific
+    flags="${flags## }"                  # Trim leading space
+    flags="${flags%% }"                  # Trim trailing space
+
+    # Retain -fPIC though
+    case "$flags" in
+    (*-fPIC*)
+        # -fPIC already included
+        ;;
+
+    (*)
+        case "$input" in
+        (*-fPIC*)
+            # Add -fPIC back in (was after the -DOPENFOAM=... content)
+            flags="$flags${flags+ }-fPIC"
+            ;;
+        esac
+        ;;
+    esac
+
+    echo "$flags"
+}
+
+
 # Export compiler settings (and flags) for CMake/configure
 # based on the values from wmake -show-compile-*
 #
 # Since "wmake -show-XX" is only available after 1904, continue to support
 # the previous env variables method (WM_CC, WM_CFLAGS, WM_CXX, WM_CXXFLAGS)
+#
+# $1 = "basic|minimal|strip" (optional)
+#
+# If the option 'basic' is provided, the OpenFOAM-specific portions of
+# the flags are stripped out. Ie, everything after "-DOPENFOAM=..."
+# but retaining '-fPIC'
+#
 exportCompiler()
 {
+    local option="$1"
     local comp flag
 
     # C compiler and flags
@@ -76,6 +114,11 @@ exportCompiler()
         export CC="$comp"
         if [ -n "$flag" ]
         then
+            case "$option" in
+                (basic | minimal | strip)
+                    flag="$(stripCompilerFlags $flag)"
+                    ;;
+            esac
             export CFLAGS="$flag"
         fi
     fi
@@ -92,11 +135,17 @@ exportCompiler()
         export CXX="$comp"
         if [ -n "$flag" ]
         then
+            case "$option" in
+                (basic | minimal | strip)
+                    flag="$(stripCompilerFlags $flag)"
+                    ;;
+            esac
             export CXXFLAGS="$flag"
         fi
     fi
 }
 
+
 # Export linker settings for CMake/configure
 exportLinker()
 {

makeParaView

@@ -127,7 +127,7 @@ USAGE
     exit 1
 }
 #------------------------------------------------------------------------------
-exportCompiler          # Compiler info for CMake/configure
+exportCompiler minimal  # Minimal compiler info for CMake/configure
 
 # Various building stages
 unset runPATCH runCONFIG runMAKE runINSTALL
@@ -367,6 +367,10 @@ Features selected
     python    ${withPYTHON:-false}
     qt        ${withQT:-false}
 ---------------------
+Compiler
+    cxx       ${CXX:-unknown}
+    flags     ${CXXFLAGS:-none}
+---------------------
 Version information
     paraview  ${ParaView_VERSION:-unknown}
     major     ${ParaView_MAJOR:-unknown}

makeVTK

@@ -103,7 +103,7 @@ USAGE
     exit 1
 }
 #------------------------------------------------------------------------------
-exportCompiler          # Compiler info for CMake/configure
+exportCompiler minimal  # Minimal compiler info for CMake/configure
 
 # Various building stages
 unset runPATCH runCONFIG runMAKE runINSTALL
@@ -293,6 +293,10 @@ Features selected
     mesa      ${withMESA:-false}
     mpi       ${withMPI:-false}
 ---------------------
+Compiler
+    cxx       ${CXX:-unknown}
+    cxxflags  ${CXXFLAGS:-none}
+---------------------
 Version information
     vtk       ${VTK_VERSION:-unknown}
     build     ${BUILD_TYPE:-unknown}