doc: add GOMIPS to source installation docs

Also close </li> tags.

Fixes #23614

Change-Id: Icabcd577ef7df43e54d2b0068ee54614ba65bea1
Reviewed-on: https://go-review.googlesource.com/90815Reviewed-by: Cherry Zhang <cherryyz@google.com>

doc/install-source.html

@@ -446,6 +446,7 @@ defaults to the parent of the directory where <code>all.bash</code> was run.
 There is no need to set this unless you want to switch between multiple
 local copies of the repository.
 </p>
+</li>
 
 <li><code>$GOROOT_FINAL</code>
 <p>
@@ -456,12 +457,14 @@ If you want to build the Go tree in one location
 but move it elsewhere after the build, set
 <code>$GOROOT_FINAL</code> to the eventual location.
 </p>
+</li>
 
 <li><code>$GOOS</code> and <code>$GOARCH</code>
 <p>
 The name of the target operating system and compilation architecture.
 These default to the values of <code>$GOHOSTOS</code> and
 <code>$GOHOSTARCH</code> respectively (described below).
+</li>
 
 <p>
 Choices for <code>$GOOS</code> are
@@ -582,6 +585,7 @@ The name of the host operating system and compilation architecture.
 These default to the local system's operating system and
 architecture.
 </p>
+</li>
 
 <p>
 Valid choices are the same as for <code>$GOOS</code> and
@@ -600,6 +604,7 @@ directory to your <code>$PATH</code>, so you can use the tools.
 If <code>$GOBIN</code> is set, the <a href="/cmd/go">go command</a>
 installs all commands there.
 </p>
+</li>
 
 <li><code>$GO386</code> (for <code>386</code> only, default is auto-detected
 if built on either <code>386</code> or <code>amd64</code>, <code>387</code> otherwise)
@@ -609,9 +614,10 @@ This controls the code generated by gc to use either the 387 floating-point unit
 floating point computations.
 </p>
 <ul>
-	<li><code>GO386=387</code>: use x87 for floating point operations; should support all x86 chips (Pentium MMX or later).
-	<li><code>GO386=sse2</code>: use SSE2 for floating point operations; has better performance than 387, but only available on Pentium 4/Opteron/Athlon 64 or later.
+	<li><code>GO386=387</code>: use x87 for floating point operations; should support all x86 chips (Pentium MMX or later).</li>
+	<li><code>GO386=sse2</code>: use SSE2 for floating point operations; has better performance than 387, but only available on Pentium 4/Opteron/Athlon 64 or later.</li>
 </ul>
+</li>
 
 <li><code>$GOARM</code> (for <code>arm</code> only; default is auto-detected if building
 on the target processor, 6 if not)
@@ -620,9 +626,9 @@ This sets the ARM floating point co-processor architecture version the run-time
 should target. If you are compiling on the target system, its value will be auto-detected.
 </p>
 <ul>
-	<li><code>GOARM=5</code>: use software floating point; when CPU doesn't have VFP co-processor
-	<li><code>GOARM=6</code>: use VFPv1 only; default if cross compiling; usually ARM11 or better cores (VFPv2 or better is also supported)
-	<li><code>GOARM=7</code>: use VFPv3; usually Cortex-A cores
+	<li><code>GOARM=5</code>: use software floating point; when CPU doesn't have VFP co-processor</li>
+	<li><code>GOARM=6</code>: use VFPv1 only; default if cross compiling; usually ARM11 or better cores (VFPv2 or better is also supported)</li>
+	<li><code>GOARM=7</code>: use VFPv3; usually Cortex-A cores</li>
 </ul>
 <p>
 If in doubt, leave this variable unset, and adjust it if required
@@ -631,6 +637,17 @@ The <a href="//golang.org/wiki/GoArm">GoARM</a> page
 on the <a href="//golang.org/wiki">Go community wiki</a>
 contains further details regarding Go's ARM support.
 </p>
+</li>
+
+<li><code>$GOMIPS</code> (for <code>mips</code> and <code>mipsle</code> only)
+<p>
+This sets whether to use floating point instructions.
+</p>
+<ul>
+	<li><code>GOMIPS=hardfloat</code>: use floating point instructions (the default)</li>
+	<li><code>GOMIPS=softfloat</code>: use soft floating point</li>
+</ul>
+</li>
 
 </ul>