android: query sysroot in ENABLE_STANDALONE=1

Running a standalone version of fbc to build with
android ndk is not recommended, but if we are,
try and query the sysroot.

If we explicitly passed in -sysroot to fbc, then
go ahead try to query gcc for the needed library
even if we aren't targeting android.

Otherwise, if we are running standalone fbc and not
targeting android and didn't pass in a -sysroot,
just return the computed library file name as was
done previously in fbc.

changelog.txt

@@ -32,6 +32,7 @@ Version 1.20.0
 - "-fpu neon" option for ARM archs (passed through to gcc).
 - -pic option (position-independent code) is now allowed on x86 (where it forces -gen gcc) and when building executables (in which case it passes -pie option to ld to produce position independent executables)
 - fbc: add '-sysroot <path>' command line option to specify the sysroot, needed by some cross-compiling toolchains
+- fbc: in fbc standalone version query gcc for library names when targetting android or -sysroot was passed explicitly to fbc
 
 [fixed]
 - github #410: give consistent floating point comparisons results involving NaNs.

src/compiler/fbc.bas

@@ -367,7 +367,20 @@ private function fbcBuildPathToLibFile( byval file as zstring ptr ) as string
 
 	found = fbc.libpath + FB_HOST_PATHDIV + *file
 
-#ifndef ENABLE_STANDALONE
+	#ifdef ENABLE_STANDALONE
+	'' running a standalone version of fbc to build with android
+	'' ndk is not recommended, but if we are, try and query the
+	'' sysroot if it wasn't already supplied.  Otherwise
+	'' if with are running a standalone fbc, just return the
+	'' computed library file name if we didn't explicitly pass
+	'' in a -sysroot
+	if( fbGetOption( FB_COMPOPT_TARGET ) <> FB_COMPTARGET_ANDROID ) then
+		if( len( fbc.sysroot ) = 0 ) then
+			return found
+		end if
+	end if
+	#endif
+
 	'' Does it exist in our lib/?
 	if( hFileExists( found ) ) then
 		'' Overrides anything else
@@ -403,7 +416,6 @@ private function fbcBuildPathToLibFile( byval file as zstring ptr ) as string
 	if( found = hStripPath( found ) ) then
 		exit function
 	end if
-#endif
 
 	function = found
 end function