Disable CPU optimizations not supported by all x86_64 systems.

--- a/cmake/modules/SIMDExt.cmake	2017-03-23 22:22:58.254071694 +0100
+++ b/cmake/modules/SIMDExt.cmake	2017-03-23 22:23:22.446848845 +0100
@@ -5,11 +5,6 @@
 # HAVE_ARM_NEON
 # HAVE_INTEL_SSE
 # HAVE_INTEL_SSE2
-# HAVE_INTEL_SSE3
-# HAVE_INTEL_SSSE3
-# HAVE_INTEL_PCLMUL
-# HAVE_INTEL_SSE4_1
-# HAVE_INTEL_SSE4_2
 #
 # SIMD_COMPILE_FLAGS
 #
@@ -85,26 +80,6 @@
       if(HAVE_INTEL_SSE2)
         set(SIMD_COMPILE_FLAGS "${SIMD_COMPILE_FLAGS} -msse2")
       endif()
-      CHECK_C_COMPILER_FLAG(-msse3 HAVE_INTEL_SSE3)
-      if(HAVE_INTEL_SSE3)
-        set(SIMD_COMPILE_FLAGS "${SIMD_COMPILE_FLAGS} -msse3")
-      endif()
-      CHECK_C_COMPILER_FLAG(-mssse3 HAVE_INTEL_SSSE3)
-      if(HAVE_INTEL_SSSE3)
-        set(SIMD_COMPILE_FLAGS "${SIMD_COMPILE_FLAGS} -mssse3")
-      endif()
-      CHECK_C_COMPILER_FLAG(-mpclmul HAVE_INTEL_PCLMUL)
-      if(HAVE_INTEL_PCLMUL)
-        set(SIMD_COMPILE_FLAGS "${SIMD_COMPILE_FLAGS} -mpclmul")
-      endif()
-      CHECK_C_COMPILER_FLAG(-msse4.1 HAVE_INTEL_SSE4_1)
-      if(HAVE_INTEL_SSE4_1)
-        set(SIMD_COMPILE_FLAGS "${SIMD_COMPILE_FLAGS} -msse4.1")
-      endif()
-      CHECK_C_COMPILER_FLAG(-msse4.2 HAVE_INTEL_SSE4_2)
-      if(HAVE_INTEL_SSE4_2)
-        set(SIMD_COMPILE_FLAGS "${SIMD_COMPILE_FLAGS} -msse4.2")
-      endif()
     endif(CMAKE_SYSTEM_PROCESSOR MATCHES "amd64|x86_64|AMD64")
   endif(CMAKE_SYSTEM_PROCESSOR MATCHES "i686|amd64|x86_64|AMD64")
 elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "(powerpc|ppc)64le")
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<div class='path'>path: <a href='/guix/log/?id=c1e7ae444a77aa5cc78a715f78843ccd178c9d6b'>root</a>/<a href='/guix/log/gnu?id=c1e7ae444a77aa5cc78a715f78843ccd178c9d6b'>gnu</a>/<a href='/guix/log/gnu/packages?id=c1e7ae444a77aa5cc78a715f78843ccd178c9d6b'>packages</a>/<a href='/guix/log/gnu/packages/docbook.scm?id=c1e7ae444a77aa5cc78a715f78843ccd178c9d6b'>docbook.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/docbook.scm?id=c1e7ae444a77aa5cc78a715f78843ccd178c9d6b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-01-14 09:24:50 -0500'>2021-01-14</span></td><td><a href='/guix/commit/gnu/packages/docbook.scm?id=2596099c257b0be5ad5cb24e98aaa1d73c3d7a55'>gnu: Add docbook-sgml-3.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/docbook.scm (docbook-sgml-3.1): New variable.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-01-14 09:24:50 -0500'>2021-01-14</span></td><td><a href='/guix/commit/gnu/packages/docbook.scm?id=81920e6d59de6d58afddb11d7acef357533f8440'>gnu: Add docbook-dsssl.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/docbook.scm (docbook-dsssl): New variable.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-01-14 09:24:49 -0500'>2021-01-14</span></td><td><a href='/guix/commit/gnu/packages/docbook.scm?id=14ac034dab923103b301d493440448e19b14d4bc'>gnu: Add docbook-sgml.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/docbook.scm (docbook-sgml): New variable.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-01-14 09:24:49 -0500'>2021-01-14</span></td><td><a href='/guix/commit/gnu/packages/docbook.scm?id=273cf0378d6ddfcf8b882decd796ad8f9699f343'>gnu: Add iso-8879-entities.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/docbook.scm (iso-8879-entities): New private variable.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2020-11-09 11:34:09 +0200'>2020-11-09</span></td><td><a href='/guix/commit/gnu/packages/docbook.scm?id=f7f92d8213961a8909f02d61fea6d135cfb449e4'>gnu: docbook: Update source URI.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/docbook.scm (docbook-xml-5)[source]: Update to new
source URI.
(docbook-xml, docbook-xml-4.4, docbook-xml-4.3, docbook-xml-4.2,
docbook-xml-4.1.2)[source]: Same.
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2020-06-14 23:15:22 +0200'>2020-06-14</span></td><td><a href='/guix/commit/gnu/packages/docbook.scm?id=bf7321cc9171a0b4145debd770666efafe0b2f24'>gnu: docbook: Add 5.0.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/docbook.scm (docbook-xml-5): New public variable.
(docbook-xml): Inherit from it.  While at it, remove trailing whitespace.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-01-21 22:39:42 +0100'>2020-01-21</span></td><td><a href='/guix/commit/gnu/packages/docbook.scm?id=8ed9be3faccb865204de46d2a8ed3e96e59281b6'>Merge branch 'staging' into core-updates</a></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-01-19 06:09:01 +0100'>2020-01-19</span></td><td><a href='/guix/commit/gnu/packages/docbook.scm?id=e6711212505f5426a6f5707445b04a14e17e55ee'>gnu: Use HTTPS for docbook.org.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/docbook.scm (docbook-xml)[home-page, source]: Use HTTPS.
(docbook-xml-4.4, docbook-xml-4.3, docbook-xml-4.2, docbook-xml-4.1.2)
[source]: Likewise.
(docbook-xsl)[home-page]: Likewise.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-01-11 18:59:23 +0100'>2020-01-11</span></td><td><a href='/guix/commit/gnu/packages/docbook.scm?id=8419a7ed44ee86e1b93b9dd1779c9ab192f98175'>gnu: dblatex: Update to 0.3.11.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/docbook.scm (dblatex): Update to 0.3.11.
</span></span></td><td>Marius Bakke</td></tr>