Fix build with GLM 0.9.9.

This patch is an amalgamation of these upstream commits:

https://github.com/LibreOffice/core/commit/953c4add8fd76d88f49a81ae4c21a1fdcc007e57
https://github.com/LibreOffice/core/commit/5f1bf6598b5725ad1e50ae9f7ec7524cc8a834fa

diff --git a/chart2/Library_chartcore.mk b/chart2/Library_chartcore.mk
index 28bc87b89057..69d4c0552636 100644
--- a/chart2/Library_chartcore.mk
+++ b/chart2/Library_chartcore.mk
@@ -23,6 +23,12 @@ $(eval $(call gb_Library_add_defs,chartcore,\
     -DOOO_DLLIMPLEMENTATION_CHARTVIEW \
 ))
 
+ifeq ($(SYSTEM_GLM),TRUE)
+$(eval $(call gb_Library_add_defs,chartcore,\
+        -DGLM_ENABLE_EXPERIMENTAL \
+))
+endif
+
 $(eval $(call gb_Library_set_precompiled_header,chartcore,$(SRCDIR)/chart2/inc/pch/precompiled_chartcore))
 
 $(eval $(call gb_Library_use_externals,chartcore,\
diff --git a/vcl/Library_vcl.mk b/vcl/Library_vcl.mk
index c1f3cc5324e7..0b684c6185a9 100644
--- a/vcl/Library_vcl.mk
+++ b/vcl/Library_vcl.mk
@@ -49,6 +49,12 @@ $(eval $(call gb_Library_add_defs,vcl,\
 	-DENABLE_MERGELIBS=$(if $(MERGELIBS),1,0) \
 ))
 
+ifeq ($(SYSTEM_GLM),TRUE)
+$(eval $(call gb_Library_add_defs,vcl,\
+        -DGLM_ENABLE_EXPERIMENTAL \
+))
+endif
+
 $(eval $(call gb_Library_use_sdk_api,vcl))
 
 $(eval $(call gb_Library_use_custom_headers,vcl,\
diff --git a/vcl/Executable_icontest.mk b/vcl/Executable_icontest.mk
index ce163303f8a4..8c917b71cd0e 100644
--- a/vcl/Executable_icontest.mk
+++ b/vcl/Executable_icontest.mk
@@ -19,6 +19,12 @@ $(eval $(call gb_Executable_use_externals,icontest,\
 ))
 endif
 
+ifeq ($(SYSTEM_GLM),TRUE)
+$(eval $(call gb_Executable_add_defs,icontest,\
+    -DGLM_ENABLE_EXPERIMENTAL \
+))
+endif
+
 $(eval $(call gb_Executable_use_api,icontest,\
     offapi \
     udkapi \
n>
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<div class='path'>path: <a href='/guix/log/?id=53477d978619153cd5df320ea3d157ddf1d5da24'>root</a>/<a href='/guix/log/TODO?id=53477d978619153cd5df320ea3d157ddf1d5da24'>TODO</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/TODO?id=53477d978619153cd5df320ea3d157ddf1d5da24&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-01-21 09:59:41 +0100'>2019-01-21</span></td><td><a href='/guix/commit/TODO?id=b93d2602f72dbbd9334a4f5c75b8721e1f2fa35a'>Update 'TODO'</a><span class='msg-avail'>...<span class='msg-tooltip'>* TODO (Installer): Add Pierre Neidhardt suggestions described here:
  https://lists.gnu.org/archive/html/guix-devel/2019-01/msg00305.html
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2019-01-17 14:11:15 +0100'>2019-01-17</span></td><td><a href='/guix/commit/TODO?id=11b68c90cd89288906c595d5c31a0413ed8a496f'>Update 'TODO'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* TODO (Installer): New section.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2016-09-01 14:57:03 +0200'>2016-09-01</span></td><td><a href='/guix/commit/TODO?id=e5cd149f681cc8d285da6c7638b70a43b333f337'>Update 'TODO'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* TODO: Remove items about guix challenge &amp; guix publish.

Signed-off-by: Vincent Legoll &lt;vincent.legoll@gmail.com&gt;
Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Vincent Legoll</td></tr>
<tr><td><span title='2014-09-16 21:11:03 +0200'>2014-09-16</span></td><td><a href='/guix/commit/TODO?id=d6af2518681643a170796ca8e267cc8097f910f1'>Remove outdated items from 'TODO'.</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2014-04-29 17:59:23 +0200'>2014-04-29</span></td><td><a href='/guix/commit/TODO?id=0423b7847baccf630349a5fc6bfa3317936467ef'>Update 'TODO'.</a></td><td>Ludovic Courtès</td></tr>