fixup! doc: use GFM footnotes in BUILDING.md

Author: Trott

BUILDING.md

@@ -181,10 +181,10 @@ Binaries at <https://nodejs.org/download/release/> are produced on:
 | linux-x64               | CentOS 7 with devtoolset-8 / GCC 8[^8]                                                                        |
 | win-x64 and win-x86     | Windows 2012 R2 (x64) with Visual Studio 2019                                                                 |
 
-[^8]: The Enterprise Linux devtoolset-8 allows us to compile
-    binaries with GCC 8 but linked to the glibc and libstdc++ versions of the host
-    platforms (CentOS 7 / RHEL 7). Therefore, binaries produced on these systems
-    are compatible with glibc >= 2.17 and libstdc++ >= 6.0.20 (`GLIBCXX_3.4.20`).
+[^8]: The Enterprise Linux devtoolset-8 allows us to compile binaries with GCC 8
+    but linked to the glibc and libstdc++ versions of the host platforms
+    (CentOS 7 / RHEL 7). Therefore, binaries produced on these systems are
+    compatible with glibc >= 2.17 and libstdc++ >= 6.0.20 (`GLIBCXX_3.4.20`).
     These are available on distributions natively supporting GCC 4.9, such as
     Ubuntu 14.04 and Debian 8.