CMake: don't enable -fPIC by default on Emscripten.

Causes weird errors on latest version.

CMakeLists.txt

@@ -183,7 +183,15 @@ set(MAGNUM_INCLUDE_INSTALL_PREFIX "."
     CACHE STRING "Prefix where to put platform-independent include and other files")
 
 option(BUILD_STATIC "Build static libraries (default are shared)" OFF)
-option(BUILD_STATIC_PIC "Build static libraries and plugins with position-independent code" ON)
+# Disable PIC on Emscripten by default (but still allow it to be enabled
+# explicitly if one so desires). Currently causes linker errors related to
+# __memory_base etc.: https://github.com/emscripten-core/emscripten/issues/8761
+if(CORRADE_TARGET_EMSCRIPTEN)
+    set(ON_EXCEPT_EMSCRIPTEN OFF)
+else()
+    set(ON_EXCEPT_EMSCRIPTEN ON)
+endif()
+option(BUILD_STATIC_PIC "Build static libraries and plugins with position-independent code" ${ON_EXCEPT_EMSCRIPTEN})
 option(BUILD_PLUGINS_STATIC "Build static plugins (default are dynamic)" OFF)
 option(BUILD_TESTS "Build unit tests" OFF)
 cmake_dependent_option(BUILD_GL_TESTS "Build unit tests for OpenGL code" OFF "BUILD_TESTS;TARGET_GL" OFF)

doc/changelog.dox

@@ -377,6 +377,9 @@ See also:
     (see [mosra/magnum#345](https://github.com/mosra/magnum/issues/345))
 -   Fixed a 64-to-32-bit conversion warning on MSVC in @ref GL::Mesh internals
     (see [mosra/magnum#352](https://github.com/mosra/magnum/issues/352))
+-   Emscripten builds now have the `-fPIC` option disabled by default as it
+    causes linker errors related to `__memory_base` on 1.38.36 (see also
+    [emscripten-core/emscripten#8761](https://github.com/emscripten-core/emscripten/issues/8761))
 
 @subsection changelog-latest-bugfixes Bug fixes